Class 12 Medical Biology - Molecular Basis Of Inheritance

What is the function of the codon AUG?

AUG is the codon which is known as the start codon. This codon codes for methionine in prokaryotes and formyl methionine in eukaryotes. This is the codon which is present as the first codon in the mRNA. This is the site from where the translation process starts to form the protein from the segment of mRNA.

Differentiate between the genetic codes :
Degenerate and Initiator

A genetic code is the sequence of the nucleotides which codes for a particular aminoacid. A genetic code is degenerate when different codon specifies the same amino acid. An initiator codon is a codon which starts the translation of proteins. It also marks the site at which the translation begins.

Protein sequences are encoded in ..........

Protein sequences are encoded in DNA.

Explain the following: Degenerate code, Unambiguous code, Universal code, Initiator code.

Degenerate code: A code in which several codewords have the same meaning. The genetic code is degenerate because there are many instances in which different codons specify the same amino acid. A genetic code in which some amino acids may each be encoded by more than one codon.
Unambiguous: Each codon specifies a particular amino acid and only that amino acid. One amino acid can be coded by several different codons. But one codon can code just for one amino acid, not more. Hence, the unambiguity of the genetic code.
Universal code: The genetic code is pretty similar in most of the organisms. It means that codon, which codes methionine in human, does the same in prokaryotes. This point is not exactly true as recently, scientists have discovered many exceptions from this rule. The genetic code is not universal, but it is still predominant.
Initiator codon or start codon: A specific set of 3 bases, "AUG", known as the "start codon", signifies the gene to start transcribing. There are 64 possible codons (four possible nucleotides at each of three positions, hence, 43 possible codons) and only 20 standard amino acids; hence the code is redundant and multiple codons can specify the same amino acid.

Match the names of triplet codons with the amino acids given under columns. Choose the answer which gives the correct combination of the alphabets of the two columns.
(a) A- s, B- t, C- q, D- r
(b) A- t, B- s, C- r, D- q
(c) A- p, B- r, C- s, D- t
(d) A- q, B- r, C- s, D- t

Codon "UUU" codes for phenylalanine; "CCC" codes for proline; "AAA" codes for lysine and "GGG" codes for glycine.

Thus, the correct answer is option B.

What is a genetic code?

The genetic code is the set of rules by which information encoded within genetic material (DNA or mRNA sequences) is translated into proteins by living cells. Biological decoding is accomplished by the ribosome, which links amino acids in an order specified by mRNA, using transfer RNA (tRNA) molecules to carry amino acids and to read the mRNA three nucleotides at a time. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries. The code defines how sequences of these nucleotide triplets, called codons, specify which amino acid will be added next during protein synthesis. With some exceptions, a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid. Because the vast majority of genes are encoded with exactly the same code, this particular code is often referred to as the canonical or standard genetic code, or simply the genetic code, though in fact some variant codes have evolved. For example, protein synthesis in human mitochondria relies on a genetic code that differs from the standard genetic code.

Following a severe accident, many charred-disfigured bodies are recovered from the site making the identification of the dead very difficult. Name and explain the technique that would help the authorities to establish the identity of the dead to be able to hand over the dead to their respective relatives.

The technique of DNA fingerprinting would help the authorities to establish the identity of the dead to be able to hand over the dead to their respective relatives.
Steps/procedure in DNA fingerprinting:
Extraction of DNA: using high speed refrigerated centrifuge.
Amplification: many copies are made using PCR
Restriction Digestion: using restriction enzymes DNA is cut into fragments.
Separation of DNA fragments: using electrophoresis agarose polymer gel.
Southern Blotting: Separated DNA sequences are transferred onto nitrocellulose or nylon membrane.
Hybridization: The nylon membrane exposed to radioactive probes.
Autoradiography: The dark bands develop at the probe site.

Explain the significance of satellite DNA in DNA fingerprinting technique.

About 3% or so of the human genome has highly repetitive sequences or simple-sequence DNA or simple sequence repeats or satellite DNA or microsatellites which are less than 10 bp long short sequences, repeated in multiples per cell. Satellite DNA, also termed as microsatellite, show relative uniformity within species and great variability between closely related species. Also, different individuals differ in a number of repeats of ssDNA. This DNA polymorphism is used in DNA fingerprinting to create DNA profiles of individuals.

State the difference between the structural gene in a transcription unit of prokaryotes and eukaryotes.

The prokaryotic structural genes are found continuously with any non-coding region while eukaryotic structural genes are divided into exons (coding regions) and introns (non-coding regions).

Name the transcriptionally active region of chromatin in a nucleus.

Euchromatin is the transcriptionally active regions of the genes. These are lightly stained region. Euchromatin is loosely stained structure which normally converts into m-RNA and helps in transcription of proteins.

(a) Construct a complete transcription unit with promoter and terminator on the basis of the hypothetical template strand given below:
(b) Write the RNA strand transcribed from the above transcription unit along with its polarity.

(a) Template Strand: 3'--Promoter - ATGCATGCATAC - Teminator 5'

coding strand (mRNA): 5' TACGTACGTATG 3'

(b) RNA transcribed: 5' UACGUACGUAUG 3'

Name the scientist who suggested that the genetic code should be made of a combination of three molecules.

(i) George Gamow suggested that the genetic code should be made up of a combination of three nucleotides.

(ii) He proposed that if 20 amino acids are to be coded by 4 bases, then the code should be made up of three nucleotides. 4$$^3$$ = 64 (4$$^2$$ = 16), which is less than 20. So, the codon was proposed to be triplet.

What would be the molar concentration of human DNA in a human cell? Consult your teacher.

The average molecular weight of a single base pair in a double-stranded DNA is 650 daltons

1 Dalton is equal to one-twelfth of the mass of a carbon-12 atom which is 1.66 x 10$$^{24}$$ grams.

Human DNA has 3.3 X 10$$^9$$ base pairs.

The molecular weight of a DNA = Number of base pairs X 650 Daltons

So, the molecular weight of Human DNA is

(3.3 X 10$$^9$$) X 650 = 2.15 X 10$$^{12}$$ daltons

which is equivalent to 3.59 X 10$$^{-12}$$ grams or 3.5 picograms.

Avogadro number of molecules is one mole. Next step is converting the amount of DNA into moles. Now in Human DNA, 3.3 X 10$$^9$$ base pairs of nucleotides are present.

So number of moles = 3.3 X 10$$^9$$ molecules / Avaggadro number

= (3.3 X 10$$^9$$) X (6 X 10$$^{23}$$)

= 5.5 X 10$$^{-15}$$

= 5.5 femtomoles of DNA

Now, by definition molarity is defined as the number of moles of solute per liter of solution

therefore, the molar concentration of human DNA can be calculated by knowing the volume of water/liquid in the cell. The volume varies in different cells. The average volume is 5 picoliter (5 X 10$$^{-12}$$ )

So, molarity of DNA in a human cell can be calculated as follows

(5.5 X 10$$^{-15}$$) / (5 X 10$$^{-12}$$) = 0.0011 M

Name the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of a DNA molecule.

The enzyme responsible for continuous and discontinuous replication of the two strands of a DNA molecule is DNA-dependent DNA polymerase.

This enzyme catalyses the polymerization only in one direction, i.e., from 5' ----> 3'. As a result, on template strand with 3' ----> 5' the replication is continuous while on the template strand with polarity 5' ----> 3' it is discontinuous.

Why is the Human Genome project called a mega project?

The human genome project is called as a mega project because there was the sequencing of each and every nucleotide base pair present in the human genome which took around 13 years for its completion. The aim of this project was to develop new technology and new information in the field of genomic studies. It was a large scale project and provide the opportunity in the field of genetics, biotechnology, and medical sciences. It provided clues regarding the understanding of human biology.

Briefly describe the following:
(a) Transcription
(b) Polymorphism
(c) Translation
(d) Bioinformatics

a) Transcription is the process in which RNA is synthesized from DNA.

Transcription is a 3 step process-

1) Initiation- RNA polymerase binds to DNA sequence called the promoter and providing the single-stranded template for transcription process.

2) Elongation- RNA polymerase reads the template strand and adds bases leading to elongation of the chain.

3) Termination- In this step terminator sequences mark the end of transcription.

b) Polymorphism is a form of genetic variation resulting in the formation of several different types of individuals among the members of one particular species. The varying sequences of nucleotides are located at different positions in a DNA helix resulting in variation and hence polymorphism in the population. Polymorphism is responsible for speciation and evolution.

c) Translation is the process in which protein is synthesized from RNA.

Translation is a 3 step process-

1) Initiation- In initiation, the ribosome assembles around the mRNA that has to be read and the first tRNA carrying the amino acid methionine

2) Elongation- In this stage the amino acid chain is elongated

3) Termination- In this stage, the synthesized polypeptide chain is released.

d) Bioinformatics is the use of information technology for collecting and analyzing complex biological data such as genetic codes, protein sequences, etc. using databases. There has been an advancement in the field of molecular biology, there is the invention of computers, scientific techniques, and instrumentation at the nano level, etc. These have helped in the development and progress in the field of bioinformatics.

Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.

There are two types of nucleic acid polymerase

1) DNA-dependent DNA polymerase: DNA polymerase enzyme adds deoxyribonucleotides to synthesize DNA using the base sequence of parental DNA strand by the process of DNA replication.
2) DNA-dependent RNA polymerase: It adds ribonucleotides primer strand to synthesize RNA using the base sequence of template DNA strand.

Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.

Watson and Crick observed that the two DNA strands are antiparallel, and have opposite polarity. This means that 5’ phosphate of one strand faces the 3’hydroxyl group of other strand and that the 5’ phosphate groups of two strands are present in opposite position. The antiparallel arrangement of two helices allows hydrogen bonding between amino and carbonyl group of complementary base pairs. This led them to the hypothesis of the semiconservative mode of DNA replication wherein two strands of DNA first separate from each other followed by copying of each template strand to form two DNA molecules each carrying one parental strand and one newly synthesized strand.

Group the following as nitrogenous bases and nucleosides:
Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

DNA is a polymer of nucleotides which are made up of sugar, a nitrogenous base and a phosphate moiety. DNA has four bases; two purines and two pyrimidines. The two purines are namely adenine and guanine and two pyrimidines are cytosine, thymine. A nucleotide unit without phosphate group is called nucleoside. Nitrogenous bases = Adenine, thymine, uracil and cytosine. Cytidine and Guanosine are the nucleosides.

Collect $$5$$ examples of palindromic sequence by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.

The palindromic sequence is a sequence of the DNA that reads the same whether read from 5’ → 3’ direction or from 3’→ 5’direction.

What is complementary base pairing?

Adenine binds to thymine and guanine binds to cytosine as they are complementary base pairs. The complementary bases can form a bond with each other. This helps to hold the two antiparallel strands of the DNA molecule together to form the helix. This is known as the complementary base pairing rule.

State the best known contribution of:
(i) Alec Jeffery
(ii) P.K. Sethi
(iii) Hugo de Vries

(i) DNA fingerprinting: DNA fingerprinting was first used for sample identification after the geneticist Alec J. Jeffreys discovered that there are patterns of genetic material that are unique to almost every individual.
(ii) P.K. Sethi developed Jaipur foot, which is prosthetic limb which is inexpensive and flexible.
(iii) Hugo de Vries is father of mutation studies. Hugo de Vries gave mutation theory and the importance of chance events i.e., mutations during evolution.

With the help of a neat and labeled diagram describe Waston and Crick's model of DNA.

DNA is a double helical structure consisting of two long strands, coiled around a ventral axis. This structure was discovered by Watson and Crick. Each strand is a polynucleotide chain, composed of many nucleotides. Each is formed by a pentose, deoxyribose sugar, a phosphate group and one nitrogen base. Sugar and nitrogenous bases are connected to each other by glycosidic bond while sugar and phosphate are joined by a phosphodiester bond, known as phosphodiester linkage. There is a complementary pairing of purines and pyrimidines. Adenine, thymine pair with double. H bond, While cytosine and guanine pair with triple H bond. H bond forms the rings in DNA molecule. The total number of purines always equals to the total number of pyrimidines, that is, A+G=T+C. This is known as Chargaff's law. One strand of DNA has 3′→5′ polarity, while opposite strand has polarity 5′→′3′. The diameter of DNA is 2 nm. The distance between two successive nucleotide is 0.34 nm. There are 10 base pairs in one complete spiral turn.

Describe Watson and Crick's model of DNA.

Complementary pairing : Nitrogen bases are double ring purines or single pyrimidines. Adenine, guanine are purines and cytosine, thymine are pyrimidines.

(1) Sugar and nitrogeneous bases are connected to each other by glycosidic bond while sugar and phosphate are joined by phosphodiester bond, known as $${3}^{\prime} \rightarrow {5}^{\prime}$$ phosphodiester linkage.

(2) There is complementary pairing of purines and pyrimidines. Adenine, thymine pair with double $$H$$ bond, while cytosine and guanine pair with the triple $$H$$ bond. $$H$$ bond form the rings in DNA molecule.

(3) Total number of purines always equals to the total number of pyrimidines, so $$A + G = T + C$$. This is known as Chargaff's law.

Polarity of strands : One strand of DNA has $${3}^{\prime} \rightarrow {5}^{\prime}$$ polarity, while opposite strand has polarity $${5}^{\prime} \rightarrow {3}^{\prime}$$. $${3}^{\prime}$$ and $${5}^{\prime}$$ are carbon atoms. Due to the fact that $${3}^{\prime} \rightarrow {5}^{\prime}$$ and $${5}^{\prime} \rightarrow {3}^{\prime}$$ direction, DNA strands are called antiparallel.

Diameter of DNA is $$2 nm$$. For one complete rotation of $${360}^{o}$$, DNA molecules cover a distance of $$3.4nm$$, whereas the distance between two successive rings are $$0.34 nm$$, that means there are $$10$$ base pairs in one complete spiral turn.

Sketch and label hair- pin model for t-RNA.

What is genetic code? Write its four salient features. Draw a diagram of t-RNA.

The relationship between the nucleotide triplets and the amino acids is called a genetic code. This determines the sequence of amino acids in the proteins that are synthesized.

Salient features of genetic code are:

(i) The codon is triplet. 61 codons code for 20 amino acids and 3 codons do not code for any amino acids, hence they function as stop codons.

(ii) One codon codes for only one amino acid, hence, it is unambiguous and specific.

(iii) The code is degenerate because some amino acids are coded by more than one codon.

(iv)The codon is read in mRNA in a contiguous fashion. There are no punctuations.

(v)The code is nearly universal.

(vi) AUG codes for Methionine (met) and it also act as initiator codon.

What is nucleosome ? Draw diagram of double stranded polynucleotide chain of DNA and explain its structure.

A nucleosome is a basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound in sequence around eight histone protein cores.

Structure of DNA:

DNA is usually a double helix and has two strands running in opposite directions. It is twisted around each other like the strands of a two-stranded rope with free ends. Each chain is a polymer of subunits called as nucleotides. Each strand has a backbone made up of deoxyribose sugar molecules linked together by phosphate groups. The 3' C of a sugar molecule is connected through a phosphate group to the 5' C of the next sugar. This linkage is also called as 3-5' phosphodiester linkage. All DNA strands are read from the 5' to the 3' end where the 5' end terminates in a phosphate group and the 3' end terminates in a sugar molecule. According to Watson and Crick model, DNA is a double helix with one turn of 34 A$$^o$$ and 10 base pairs per turn. Thus, the distance between adjacent bases is 3.4 A$$^o$$. The helix diameter is 20A$$^o$$. The base pairing of opposite strands is stereochemically selective, Adenine always pairing with Thymine, and Guanine with Cytosine. Two and three hydrogen bonds are formed in A-T and G-C base pairs, respectively. The attachment of bases to the backbone sugars through glycosidic bonds is asymmetrical. This results in the formation of two different grooves on opposite sides of the base pairs, the major and minor grooves.

Draw a neat labelled diagram of the hair pin model of t-RNA?

$$\textbf{Solution:}$$

$$\bullet$$ The tRNA molecule actually contains three hairpin loops that form the shape of a three-leafed clover consisting of different parts.

$$\bullet$$ One of these hairpin loops contains a sequence called the anticodon, which recognizes and decodes the mRNA molecule three nucleotides (one codon) at a time during translation.

$$\bullet$$ The 3' end carries the amino acid that forms a bond with the OH- group.

$$\bullet$$ It consists of three loops that are: D-loop, T-loop, and anticodon loop.

$$\bullet$$ The clover-leaf structure supports the eventual connection between every codon, anti-codon, and amino acid.

2217733_602160_ans_ee42ef26e7064d278705ea0a00449517.png

Write down the four salient features of genetic code.

The salient feature of genetic code are as follows:

(i) The codon is a triplet. 61 codons code for 20 amino acids and 3 codons do not code for any amino acids, hence they function as stop codons.

(ii) One codon codes for only one amino acid, hence, it is unambiguous and specific.

(iii) The code is degenerate because some amino acids are coded by more than one codon.

(iv)The codon is read in mRNA in a contiguous fashion. There are no punctuations.

(v)The code is nearly universal.

(vi) AUG codes for Methionine (met) and it also act as initiator codon.

Give the application of DNA fingerprinting technique.

The applications of DNA fingerprinting technique are

(i) For identification of a suspect in a crime

(ii) For establishing paternity and/or maternity accurately

What is human genome project (HGP)?

Human genome project was discovered by Francis Collins and Roderick. Human Genome Project involves the human genome programmes to understand the genetic composition and the genetic information that make up a human and identifying and mapping all of the genes of the human genome from both a physical and a functional standpoint.

Write the important features of genetic code.

The salient feature of genetic code are as follows:

(i) The codon is a triplet. 61 codons code for 20 amino acids and 3 codons do not code for any amino acids, hence they function as stop codons.

(ii) One codon codes for only one amino acid, hence, it is unambiguous and specific.

(iii) The code is degenerate because some amino acids are coded by more than one codon.

(iv)The codon is read in mRNA in a contiguous fashion. There are no punctuations.

(v)The code is nearly universal.

(vi) AUG codes for Methionine (met) and it also act as initiator codon.

What is DNA fingerprinting? Write any four applications of DNA fingerprinting.

DNA fingerprinting is a technique which is used to determine the regions which are specific to an individual. There are VNTRs present in the genome of every organism which can be determined by using this technique.

Application of DNA fingerprinting technique:

DNA polymorphism can be studied. The position and the number of VNTRs are revealed during DNA fingerprinting.
This technique can be useful in the identification of suspect since it is very remote possibility to have two individuals same repeats of satellite DNA throughout the genome except they share a biological relationship.
Restriction enzymes of genome produce the restriction fragments length polymorphisms, or RFLPs depending on the location of restriction sites which are then sorted by gel electrophoresis followed by southern blotting.
The blots of the suspect and of the sample from the crime scene are compared for sequence homology using radioactive probes.
This can also be used for paternity testing in the case of lost child.
This method is used in various fields of forensics.

What is DNA Library?

A DNA library is a collection of DNA fragments, which contains all the sequences of a single organism. A collection of clones that includes all the DNA sequences of a given species is called as a genomic DNA library. These libraries can be used to study the genes for the production of respective genes.

In a typical DNA molecule, the proportion of thymine is $$20\%$$ of the N bases. Find out the percentages of other N bases.

According to the rule given by Chargaff, A + G = C + T.

Adenine (A) will always pair with Thymine (T). This means that A = T.

Cytosine (C) will always pair with Guanine (G). This means that C = G.

Since the proportion of thymine T = 20%, so, A = 20%.

G + C = 100 - 40% = 60%

So, G = 30% and C = 30%.

Therefore, the answer is T = 20%, A = 20%, G = 30% and C = 30%.

In a typical DNA molecule, the proportion of thymine is $$30$$% of the $$N$$ bases. Find out the percentage of other $$N$$ bases.

According to the rule given by Chargaff, A + G = C + T.

Adenine (A) will always pair with Thymine (T). This means that A = T.

Cytosine (C) will always pair with Guanine (G). This means that C = G.

Since the proportion of thymine T = 30%, so, A = 30%.

G + C = 100 - 60% = 40%

So, G = 20% and C = 20%.

Therefore, the answer is T = 30%, A = 30%, G = 20% and C = 20%.

List the salient features of human genome project.

The Human Genome Project is an international research project with the goal of determining the sequence of human DNA and of identifying it,

Salient features of Human genome project:

(i) U.S. Department of Energy and National Institute of Health embarked and coordinated on the project of sequencing human genome called HGP or Human Genome Project.

(ii) HGP is a mega project involving a lot of money, most advanced techniques, numerous computers and scientists at work.

(iii) HGP was closely associated with rapid development of a new era in biology called as Bioinformatics.

Define stop codon. Write the codons.

The stop codon is the code of the three nucleotides in the segment of the mRNA which results in the termination of the activity of the ribosome during the process of translation. The protein which is formed gets released when the ribosome reaches the stop codon. This codon is also known as the termination codon. The codons UAG, UGA and UAA are known as the stop codons.

Explain 'Wobble hypothesis' with the help of a suitable diagram.

Wobble hypothesis states the degeneracy of the genetic code. The pairing of the third base varies according to the base at the third position, for example, G may pair with U. The conventional pairing (A = U, G = C) is called Watson-Crick pairing and the second abnormal pairing is called wobble pairing.

Answer in 200 to 250 words:
Enumerate the salient features of Human Genome Project (HGP).

In the year 1990, the Human Genome Project was started by National Human Genome Research Institute (NHGRI) in the United States in collaboration with the Department of Energy.

The aim was to determine the sequence of nucleotides in the entire human genome. Genome sequencing can be used in identification of disease-causing genes and their elimination, the introduction of new genes that code for a desired proteins and in exploiting polymorphism to compare DNA samples from two individuals.

Describe the process of DNA replication with the help of a diagram.

DNA replication is the basis of biological inheritance in all living beings.
The process gives rise to two identical replicas of the original DNA molecule.
Replication begins at specific locations in the genome and the unwinding of DNA occurs with the help of the enzyme helicase and gyrase.
The new strand synthesis takes place in the 5'-3' direction by the enzyme DNA polymerase.
The synthesis of new strands is bidirectional. One of the strand is known as the leading strand and the other is the lagging strand where there is need of an RNA primer to initiate the process.
The two copies of the DNA which are synthesized are equally distributed to the two new cells which are formed after cell division.
This process takes place in the S-phase of the interphase.

Explain replication of bacteriophage with the help of a suitable diagram.

Steps in replication of bacteriophage are-

1) Attachment of phage to E-coli.

2) Breakdown of bacterial chromosome by phage.

3) Replication of phage chromosome using bacterial materials.

4) Expression of phage genes to produce phage structural components.

5) Assembly of progeny phage particles.

6) Release of progeny phages outside the bacterium by lysis.

Newly formed DNA copies may not be identical at times. Gives one reason.

The DNA copies are produced during the process of cellular division. The new DNA copies which are synthesised during replication may not be identical to the original one, This may be due to the introduction of the mutations during the replication process. Mutations are random genetic changes. There are repair mechanisms which correct the mutations incorporated in the DNA. However, there many be some errors which remain in the new DNA. So, it is not necessary that the copies may be identical at times.

What is DNA replication? Write the chemical composition of DNA.

DNA replication is the basis of biological inheritance in all living beings. The process gives rise to two identical replicas of the original DNA molecule. Replication begins at specific locations in the genome and the unwinding of DNA occurs with the help of the enzyme helicase and gyrase. The new strand synthesis takes place in the 5'-3' direction by the enzyme DNA polymerase. The synthesis of new strands is bidirectional. The two copies of the DNA which are synthesised are equally distributed to the two new cells which are formed after cell division. This process takes place in the S-phase of the interphase. The DNA molecule is a double helix with two strands running in the opposite directions. There are complementary base pairs which are present in the two strands which bind and allow the double helical molecule to be formed. There are four nitrogen bases, adenine (A), thymine (T), cytosine (C) and guanine (G). The nucleotide contains the deoxyribose sugar, phosphate and nitrogen base.

Differentiate between the genetic codes:
Unambiguous and Universal

Unambiguous is the term used for the genetic code because there are many codons which can code for the same amino acid.

Universal is the term for the genetic code that the same genetic code codes for the same amino acids in all the organisms. The code is universally accepted.

Rearrange B and C according to the data given in A.
A B C
Nucleic Acids Sugar Nitrogen Base
DNA a) Ribosome x) Uracil
RNA b) Deoxyribose y) Adenine
c) Ribose z) Thymine

A	B	C
Nucleic Acids	Sugar	Nitrogen Base
DNA	Deoxyribose	Adenine Thymine
RNA	Ribose	Uracil Adenine

Diagrammatic representation of 'central dogma' is given below :
Observe the diagram carefully and redraw it making appropriate corrections.
$$\circlearrowleft DNA \xrightarrow [] {translation} mRNA \xrightarrow [] {transcription} Protein $$

The image explains the central dogma with the proper corrections.

Find the odd one. Write down the common features of others.

Adenine, Cytosine, Thymine, Uracil.

Uracil is the nitrogenous base found only in RNA instead of Thymine.

The other three Adenine, Cytosine and Thymine are found in DNA.

"Prediction of the sequence of amino acids from the nucleotide sequence in mRNA is very easy, but the exact prediction of the nucleotide sequence in mRNA from the sequence of amino acids coded by mRNA is difficult". Which properties of the genetic code is the reason for the above condition? Explain.

The genetic code is degenerate. There are more than one codon which can code for the same amino acids. So it is difficult to trace the nucleotide sequence which is present on the mRNA with the help of the amino acid sequence.

List the two methodologies which were involved in human genome project. Mention how they were used.

The human genome project is the project of mapping of the human genome which is about 3x10$$^9$$ bp. The methodology that used in this project was expressed sequence tags and sequence annotation. Expressed sequence tags were used to identify all the genes that are expressed as RNA and sequence annotation that focused on the sequencing of total DNA from the cell and converted into random fragments of relatively smaller size.

Given below is the transcribed strand of the DNA duplex :3'-TACCGATCCGAGCTG-5'
(a)Draw the complementary DNA polynucleotide chain
(b)Construct the RNA molecule, which will'be transcribed.

(a) 5'-ATGGCTAGGCTCGAC-3'

(b) 3'-AUGGCUAGGCUCGAC-5'

Briefly discuss the structure and functions of DNA.

Structure of DNA: Watson and Crick suggested that DNA is made up of two strands that twist around each other to form a right-handed DNA. The two DNA strands are anti-parallel. The backbone of DNA is made up of sugar and phosphate. There are approximately 10 nitrogenous bases per turn in DNA. It has major grooves and minor grooves. Nitrogenous bases are purine and pyrimidine. Purines are adenine (A) and cytosine (C). Pyrimidines are Thymine (T) and guanine (G). In DNA, there are two hydrogen bonds between adenine (A) and thymine (T) and three hydrogen bonds between cytosine (C) and guanine (G). These are called as complementary base pairs.

Function of DNA: It stores the genetic information. The information is transmitted from parents to children through the process of DNA replication. When DNA is replicated, it makes a duplicate copy of its DNA, then the cell divides, resulting in the correct distribution of one DNA copy to each resulting cell. It is also used as a source of nucleosides and nucleotides.

What do you understand by the antiparallel arrangement of DNA strands?

The two DNA chains are antiparallel that is, they run parallel but in opposite directions. In one chain the direction is 5' -> 3' while in the opposite one it is 3'-> 5'. The two chains are held together by hydrogen bonds between their bases.

Match the triplet codons mentioned in list I with their amino acids mentioned in listcolumn II and select the correct option from the given codes.

A. GGG	2. Glycine
B. UUU	4. Phenylalanine
C. CCC	1. Proline
D. AAA	5. Lysine

Codons are a triplet of nucleotide, which undergoes translation at the ribosome with the tRNA to form amino acids.

The correct pairing of the codon and the amino acid they form is given in the table.

'Genetic code is unambiguous and specific.' Explain.

Genetic code is inter-relationship between nucleotides sequence of DNA or mRNA and amino acids sequence in a polypeptide. It is a mRNA sequence containing coded information for one amino acid and consists of 3 nucleotides. One codon codes for only one amino acid, hence a genetic code is unambiguous and specific. Only GUG is ambiguous codon, it normally codes for valine but at initiating position as well as codes for methionine.

The double helix model for DNA was proposed by .......... and ..........

The double helix model for DNA was proposed by Watson and Crick.

Chemical analysis has shown that the number of adenine molecules in a DNA sample is always the same as the number of molecules of ..........

Chemical analysis has shown that the number of adenine molecules in a DNA sample is always the same as the number of molecules of thymine as both are paired through hydrogen bonds. The number of cytosine molecules is equal to the number of thymine molecules.

Very short answer type.
Name two scientists who were awarded Nobel Prize for deciphering DNA structure.

James D. Watson, and Francis H. C. Crick.

Write the importance of DNA.

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. DNA and ribonucleic acid (RNA) are nucleic acids; alongside proteins, lipids and complex carbohydrates.

DNA is important due to the following reasons:

1) DNA plays a crucial role in research, and also to carry out different tasks pertaining to fields such as forensic science, genealogy, agriculture, medicine, etc.

2) Through the assessment of DNA, the paternity of a child can be identified, which has a significant effect on the child's upbringing and his or her life.

3) DNA is essential for the life of the human cell.

4) DNA codes for all the cell proteins that make life possible. The cell transcribes DNA into RNA, which it then translates into proteins. These include the enzymes, hormones and structural proteins that each cell needs.

5) Required for reproduction.

6) Cell division is essential for an organism to grow, but, when a cell divides, it must replicate the DNA in its genome so that the two daughter cells have the same genetic information as their parent.

Double-helical structure is found in ..........

Double helical structure is found in DNA.

Differentiate between nucleoside and nucleotide.

Following are the differences between nucleoside and nucleotide : -

	Nucleoside	Nucleotide
1	A nucleoside is a compound formed by the union of a nitrogen base with a pentose sugar.	A nucleotide is a compound formed by the union of a nitrogen base, a nitrogen sugar and phosphate.
2	It is a component of nucleotide.	A nucleotide is formed through phosphorylation of nucleotide,
3	It is slightly basic in nature.	A nucleotide is acidic in nature.
4	Example - Adenosine.	Example: - Adenylic acid.

What name is applied to the model for the molecular structure of DNA?

Double helix form is the name applied to the model for the molecular structure of DNA.

Why is the Human Genome Project called a mega project?

Imagine the magnitude and the requirements for the project. Human genme has approx. $$3 \, \times \, 10^9$$ bp, and the total estimated cost of sequencing would be approx $ 9 billion. Further, the enormous amount of data generated would necessitate the use of high speed computational devices for data storage and retrieval and analysis.

What is transformation?

The phenomenon by which DNA isolated from one type of cell, when introduced into another type, is able to bestow some of the properties of former to the latter.

Give reasons Genetic code is universal.

All known living systems use nucleic acids and the same three-base codons to direct the synthesis of proteins from amino acids. The mRNA codon UUU, for example codes for phenyl alanine in all cells of all organisms. Hence, genetic code is universal.

The genetic code is said to be a triplet code. What does this mean and why is it important?

The genetic code is defined as the structure of nitrogen bases and mRNA molecule which contains the information for the synthesis of the protein molecule.

A single amino acid is specified by a sequence of three nucleotides in the mRNA. Due to this triplet nature, it consists of 64 codon. There are 20 amino acids and they are coded by 64 codons.

The genetic code is of importance because it codes the amino acids and helps in protein formation.

How do a code, codon, and anticodon differ?

The structure of nitrogen bases in mRNA molecule which contains the information for the synthesis of the protein molecule is known as genetic code.

A codon is the sequence of nitrogenous bases and mRNA which codes for the single amino acid. A single amino acid is determined by sequence of the nitrogenous bases which is known as a triplet code.

The anticodon sites which is present on t RNA has three unpaired bases also known as a triplet of bases whose sequence is complementary with mRNA.

(a) In an experiment Griffith introduced heat-killed S-strain bacteria Streptococcus into a mouse along with live R-strain bacteria. The mouse died but the scientist recovered living S-strain bacteria from the dead mouse. Explain the conclusion Griffith arrived at after the experiment.
(b) Explain MacLeod, McCarty and Averys work that followed Griffith's experiment. State the conclusion they arrived at.

After the experiment, Griffith arrived at the conclusion that the R strain bacteria take up something from the environment which converts them into the S strain bacteria. this causes a violent nature in the bacteria. Giffith thus discovered Transformation.

MacLeod, McCarty and Avery came to the conclusion and after a series of tests following Griffith they found that the genetic material is the DNA.

(a) Explain the experiment performed by Griffith on Streptococcus pneumoniae. What did he conclude from this experiment?
(b) Name the three scientists who followed up Griffiths experiments.
(c) What did they conclude and how?

(a) In 1928, Fredrick Griffith, in a series of experiments with Streptococcus pneumoniae (bacterium responsible for pneumonia), witnessed a miraculous transformation in the bacteria. During the course of his experiment, a living organism had changed in physical form.

When Streptococcus pneumoniae bacteria are grown on a culture plate, some produce smooth shiny colonies (S) while others produce rough colonies (R). This is because the S strain bacteria have a mucous (polysaccharide) coat, while R strain does not. Mice infected with the S strain (virulent) die from pneumonia infection but mice infection with the R strain do not develop pneumonia.

S strain injected into mice, mice die.

R strain injected into mice, mice live.

Griffith was able to kill bacteria by heating them. He observed that heat-killed S strain bacteria injected into mice did not kill them. When he injected a mixture of heat-killed S and live R bacteria, the mice died. Moreover, he recovered living S bacteria from the dead mice.

He concluded that the R strain bacteria had somehow been transformed by the heat-killed S strain bacteria. Some 'transforming principle', transferred from the heat-killed S strain, had enabled the R strain to synthesise a smooth polysaccharide coat and become virulent. This is due to the transfer of the genetic material.

(b)The three scientists who followed up Griffith experiment are Ostwald Avery, Colin MacLeod and McCarty.

(c)They purified biochemicals (proteins, DNA, RNA, etc.) from the heat-killed S cells to see which ones could transform live R cells into S cells. They discovered that DNA alone from S bacteria caused R bacteria to become transformed.

They also discovered that protein-digesting enzymes (proteases) and RNA-digesting enzymes (RNases) did not affect transformation, so the transforming substances was not a protein or RNA. Digestion with DNase did inhibit transformation, suggesting that the DNA caused the transformation. They concluded that DNA is the hereditary material, but not all biologists were convinced.

(a) How many codons code for amino acids and how many do not?
(b) Explain the following giving one example of each
(i) Unambiguous and specific codon
(ii) Degenerate codon
(iii) Universal codon
(iv) Initiator codon.

There are total 64 codons that code for a total of 20 amino acids. Out of the 64 codons, 61 code for the amino acids and 3 are termination or non-sense codon.

The unambiguous and specific codon is a property of the genetic code that one codon specifies for one amino acid only.

A codon specifies the same amino acid in all organism from viruses to a human being this is universal.

Initiation codon- the synthesis of the polypeptide chain is initiated by initiation codon it is AUG which is methionine.

Degenerate codons are the ones that code for more than one amino acid.

What is amplification with reference to DNA fingerprinting?

Use of polymerase chain reaction, amplification of targeted nucleotide sequence as a means of identifying microorganisms for the diagnostic and epidemiologic purpose has initiated a transformation in laboratory-based approach to infectious disease diagnosis and was the subject.

Describe the experiment performed by Griffith. What conclusions did he infer from his observations?

Griffith introduced heat-killed S-strain bacteria Streptococcus into a mouse along with living R-strain bacteria. The mouse died but the scientist recovered living S-strain bacteria from the dead mouse.

What is genetic code? Mention the essential qualities for a universal genetic code.

The structure of nitrogen base in mRNA in a molecule which contains the information for the synthesis of the protein molecule.

The salient features of the genetic code are-

Triplet- single amino acid is specified by a sequence of three nucleotides in mRNA which is known as codons.

A codon specifies the same amino acid in all organism from viruses to a human being this is universal.

These are commaless- there is no pause, so it is continuously.

Non-overlapping between adjacent nucleosides.

Initiation codon- the synthesis of the polypeptide chain is initiated by initiation codon it is AUG which is methionine.

Termination codons are also known as a nonsense codon.

Degeneracy single amino acids are specified by many codons which are known as degeneracy.

Why are there 64 different codons for 20 different amino acids?

The structure of nitrogen base in mRNA in a molecule which contains the information for the synthesis of the protein molecule.

The salient features of the genetic code are-

Triplet- single amino acid is specified by a sequence of three nucleotides in mRNA which is known as codons.

Degeneracy- single amino acids are specified by many codons which are known as degeneracy.

There are 20 amino acids that are coded by 64 codons. Many codons are degenerate.

Codon AUG has dual function. Justify.

Codon AUG has dual function:

(i) It codes for methionine amino acid into the internal protein positions.

(ii) It also act as initiation codon during the translation process.

List the salient features of human genome.

Salient features of Human Genome:

a. Human genome contains 3164.7 million nucleotide bases.

b. Total number of genes are about 30,000.

c. Average gene consists of 3000 bases but sizes vary. Largest known human gene (dystrophin on X-chromosome) contains 2.4 million bases.

d. About 99.9% nucleotide bases are identical in all people. It is that 0.1% which makes each one unique.

e. Functions of over 50 of discovered genes are unknown.

f. Chromosome I has most genes (2968) and Y has the least genes (231).

g. Repetitive sequences are stretched of DNA sequences that are repeated many times. They make the largest portion of DNA. They have no direct coding functions but they shed light on chromosome structure, dynamics and evolution.

h. There are about 1.4 million locations where single-base DNA differences (SNPs- Single nucleotide polymorphism) occur in humans.

What is the diagram representing?

histones function as spools for the thread-like DNA to wrap around. Under the microscope in its extended form, chromatin looks like beads on a string. The beads are called nucleosomes. Each nucleosome is made of DNA wrapped around eight histone proteins that function like a spool and are called a histone octamer.

So the diagram is representing the wrapped DNA around the histone octamer.

Mention the $$DNA$$ sequence coding for serine and the anticodon to $$tRNA$$ for the same amino acid.

The codon on the DNA sequence which code for serine and the anti-codon are:-

CODON	ANTI -CODON
UCU	AGA
UCC	AGG
UCA	AGU
UCG	AGC
AGU	UCA

Name the parts a, b and c.

(a)Histone octamer

(b)DNA

(c)H1 histone

Mention the contribution of genetic maps in human genome project.

Gene mapping describes the methods used to identify the locus of a gene and the distances between genes. The Human Genome Project was an international scientific research project with the goal of determining the sequence of nucleotide base pairs that make up human DNA, and of identifying and mapping all of the genes of the human genome from both a physical and a functional standpoint. So genetic mapping help is HGP in the following ways:-

 Genetic mapping has been used in finding the exact location of the chromosomes.

 The mapping of DNA also helps in the detection of the inherited disease.

How do histones acquire positive charge?

Histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are positively charged molecule due to the presence of basic amino acids which include arginine and lysine which give it the positive charge.

Give salient features of human genome.

Salient features of Human Genome:

a. Human genome contains 3164.7 million nucleotide bases.

b. Total number of genes = about 30,000.

c. Average gene consists of 3000 bases, but sizes vary. Largest known human gene (dystrophin on X-chromosome) contains 2.4 million bases.

d. 99.9 nucleotide bases are identical in all people. 0.1 is what makes each of us unique.

e. Functions of over 50 of discovered genes are unknown.

f. Chromosome I has most genes (2968) and Y has the fewest (231).

g. Less than 2 of the genome codes for proteins.

h. Repeated sequences make up very large portion of human genome. Repetitive sequences are stretched of DNA sequences that are repeated many times. They have no direct coding functions, but they shed light on chromosome structure, dynamics and evolution.

i. About 1.4 million locations where single-base DNA differences (SNPs- Single nucleotide polymorphism or 'snips') occur in humans.

Why are some untranslated sequences of bases seen in $$mRNA$$ coding for polypeptide? Where exactly are they present on $$mRNA$$?

The 5′ untranslated region (5′ UTR) (also known as a leader sequence or leader RNA) is the region of an mRNA that is directly upstream from the initiation codon. This region is important for the regulation of translation of a transcript by differing mechanisms in viruses, prokaryotes, and eukaryotes.

Explain the mechanism of DNA replication. Highlight the role of enzymes in the process.

DNA replication is the biological process, in which cellular machinery produces two identical replicas of DNA from one original DNA molecule. DNA replication, like all biological polymerization processes, proceeds in three enzymatically catalyzed and coordinated steps: initiation, elongation, and termination.

Initiation: This process is initiated at particular points in the DNA, known as "origins", which are targeted by initiator proteins. Once the origin has been located, these initiators recruit other proteins and form the pre-replication complex, which unwinds the double-stranded DNA.
Elongation: Primase adds RNA primers to the template strands. The leading strand receives one RNA primer while the lagging strand receives several. The leading strand is continuously extended from the primer by a DNA polymerase, while the lagging strand is extended discontinuously from each primer forming Okazaki fragments. RNase removes the primer RNA fragments. When this is complete, a single nick on the leading strand and several nicks on the lagging strand can be found. Ligase works to fill these nicks in, thus completing the newly replicated DNA molecule.
Termination: requires that the progress of the DNA replication fork must stop or be blocked. Termination at a specific locus, when it occurs, involves the interaction between two components: (1) a termination site sequence in the DNA, and (2) a protein which binds to this sequence to physically stop DNA replication. In various bacterial species, this is named the DNA replication terminus site-binding protein, or Ter protein.

New DNA is made by enzymes called DNA polymerases, which require a template and a primer (starter) and synthesize DNA in the 5' to 3' direction.

DNA replication requires other enzymes in addition to DNA polymerase, including DNA primase, DNA helicase, DNA ligase, and topoisomerase, as mentioned in the above steps

Two nucleotide are linked through $$3'-5'$$ phosphodiester linkage to from dinucleotide. Explain.

DNA is a double helix structure in which two strands are linked together by hydrogen bonds between complementary bases. The two strands runs in opposite direction. Two nucleotide are linked through 3′−5′ phosphodiester linkage to from dinucleotide. In this, the phosphodiester bond is present between the 3' carbon atom of one sugar molecule and the 5' carbon atom of another sugar molecule.
964560_1048777_ans_2c6e1b8581b44f8ab2026878a1d2156c.png

964560_1048777_ans_2c6e1b8581b44f8ab2026878a1d2156c.png

Draw and explain the clover leaf life structure of nucleic acid molecule

As per the clover leaf model, the single chain of tRNA is folded on itself to form five arms. As a result of this folding, the 3' end and 5' end lie adjacent to each other. Each arm consists of a basal stalk, and a loop.

The double stranded stalks show the typical base pairing. There could be an exceptional mismatch. The loops do not have base pairing. One of the arms which does not have a loop is called the acceptor as this is the binding site for amino acids. The second arm is called the DNA arm or D loop. This has a synthetase site which recognizes the amino acid activating enzyme. The fourth is a variable arm; it has a stem, but the loop may or may not be present. The T arm or Tψc-loop has a ribosome recognition site.

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What is the importance of copying of DNA during reproduction?

DNA determines the body organization of an individual.
The DNA that gets transferred from parents to children makes them look similar.
DNA copying is important for reproduction.
Some other additional copies of DNA are made during replication necessary for the formation new cells formed after cell division.
Moreover, some minor alterations during DNA replication are responsible for bringing variations in the population.

Write the important features of genetic code.

A codon is a triplet of nucleotides (adenine, cytosine, guanine, thymine or uracil).
There are 64 possible combinations of three-nucleotide sequences.
61 of these code for 20 different amino acids.
Three codons do not code for any amino acids. They function as stop codons to end protein synthesis. These are UAG, UGA, and UAA.
Each codon codes for only one amino acid, hence, it is unambiguous and specific.
Some amino acids are coded for by more than one codon, hence the genetic code is degenerate. Most of this degeneracy involves the third nucleotide of a codon.

What are satellites in a genome? Explain their role in DNA fingerprinting.

Satellite genome is a part of genome that contains highly repetitive DNA sequence. Each individual has different but specific lengths of DNA satellites. This DNA satellites in a genome forms the basis of DNA fingerprinting. These are inherited from parents to offspring and can be used for determing the paternity. Satellites are of two types, minisatellites and microsatellites.

Write about the methodologies of human genome project.

There were three steps involved in the methodology of the human genome project as follows:

1. Generation of chromosome mapping through the physical mapping, wherein DNA and genes were identified on the chromosomes, and genetic mapping, wherein the genes were arranged on the basis of linkage.

2. Sequencing of DNA through whole genome shotgun and cDNA sequencing method, in order to know the sequence of base pairs on the DNA.

3. Annotation of the sequence by identifying the genes causing genetic disorders and sequence variation in repetitive sequences

Explain Watson and Crick's model of DNA.

The following points explain the model of DNA as proposed by Watson and Crick:

1. DNA is made up of double helix made up of polynucleotide chains that are coiled with each other in a right-handed fashion.

2. The two strands are anti-parallel to each other. One stand runs in 5'-3' polarity and other runs in 3' to 5' polarity.

3. The deoxyribose sugar and the phosphate group attached to it form the backbone of the polynucleotide strands.

4. The nitrogenous bases attached with deoxyribose sugar through glucosidic bonds form the inner core.

5. The nitrogenous bases of the two strands form hydrogen bonds as per their complementary, such that Adenine forms two H-bonds with Thymine and Guanine forms three H-bonds with cytosine.

6. The diameter of the DNA is 20nm and the bases are at 0.34 nm. There are 10 base pairs per turn and the length of the turn is 3.4 nm.

7. The helix shows a minor groove and a major groove.

What should be the nature of genetic code if there would have been $$65$$ amino acids?

The nature of genetic code doesn't depend on the number of amino acids. It remains the same universally. There are 20 types of amino acids and 2 more amino acids are recently discovered. These are selenocysteine and pyrrolysine, which codes for UGA and UAG respectively.

Genetic code is unambiguous means each codon specifies one amino acid only. Example: GUC codes for only valine and no other amino acid.

Genetic code is degenerate means, many codons can code for one amino acid. Example: GUU, GUA and GUG all code for valine.

In DNA you find which type(s) of bond?

The DNA double helix polymer of nucleic acid held together by nucleotides which base pair together. In B-DNA, the most common double helical structure found in nature, the double helix is right-handed with about 10–10.5 base pairs per turn. The backbone of the DNA is made up of phosphodiester bonds and the two strands are connected to each other by hydrogen bonds. There are two hydrogen bonds in A-T base pairing and three hydrogen bonds in G-C base pairing.

A DNA molecules measuring $$680A^o$$ contains ______

The length of a base pair in B-DNA is 3.4 angstrom. So, when the total length of the DNA is 680 Angstrom, the total number of base pairs will 680/3.4 = 200. Thus, the total number of base pair is 200.

What is DNA fingerprinting ? Describe various steps involved in the same.

DNA fingerprinting is a method used to identify an individual from a sample of DNA by looking at unique patterns in their DNA. Steps involved in DNA fingerprinting are:

(i) isolation of DNA

(ii) digestion of DNA by restriction endonucleases

(iii) separation of DNA fragments by electrophoresis

(iv) transferring (blotting) of separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon

(v) hybridisation using labelled VNTR probe

(vi) detection of hybridised DNA fragments by autoradiography.

What are termination codons?

During translation, the polypeptide chain ends with the signal of codons and those codons are called nonsense codons or termination codons. UAG, UAA, and UGA are the three stop codons which terminate the polypeptide chain process.

Define transcription.

$$\textbf{Solution:}$$

$$\bullet$$ Transcription is the process by which the information in a strand of DNA is copied into a new molecule called messenger RNA (mRNA).

$$\bullet$$ The segments of DNA are transcribed into RNA molecules that encode proteins are said to produce messenger RNA.

$$\bullet$$ This mRNA encodes genes that are translated into protein by the process of translation.

$$\bullet$$ Other segments of DNA are copied into RNA molecules called non-coding RNAs.

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Give one significant contribution of each of the following scientists:
Alec Jeffery

Alec Jeffreys is related with the Discovery of DNA Fingerprinting in 1984. He then studied hereditary diseases in families. He focused on methods to resolve paternity and immigration disputes by demonstrating the genetic links between individuals.

The discovery of such a weird phenomenon certainly raises questions about how genomes evolve, and what could have been missed from existing genome sequencing projects. Perhaps we need to go back and take a closer look.

Genome explanation: The way toward recognizing the areas of qualities and the majority of the coding locales in a genome and figuring out what those qualities do. A comment (independent of the unique circumstance) is a note included by the method for clarification or editorial. When a genome is sequenced, it should be commented on to comprehend it.

Independent from anyone else, not a ton. Genome sequencing is regularly contrasted with "deciphering," however an arrangement is still particularly in code. It might be said, a genome grouping is just a long series of letters in a puzzling dialect. So sequencing the genome doesn't quickly expose the hereditary insider facts of a whole species. Indeed, even with an unfinished copy of the human genome grouping close by, much work stays to be finished. Researchers still need to decipher those series of letters into a comprehension of how the genome functions: what the different qualities that make up the genome do, how unique qualities are connected, and how the different parts of the genome are composed. That is, they need to make sense of what those letters of the genome grouping mean.

How does a degenerate code differ form an unambiguous one?

In a degenerate code, different words or terms have the same meaning. The genetic code is degenerate because many codons may code for the same amino acid.
In an unambiguous code, one codon specifies one amino acid only.

Describe the DNA structure worked by Watson and Crick.

DNA stands for deoxyribonucleic acid

Watson and Crick gave the double helical structure of DNA. It is seen that DNA is composed of the different type of nucleotides that combined together. Watson and Crick suggested that in a DNA molecule there are two such polypeptide chains arranged antiparallel or in an opposite direction that is one polypeptide chain runs in 5'-3'direction and other in 3'-5' direction.

The two strands of the double helix are antiparallel due to a phosphodiester bond.

The polynucleotide chain has a sugar-phosphate backbone with nitrogenous bases directed inside the helix.

Mention two approaches used while sequencing human genome.

BAC to BAC sequencing	whole genome shotgun sequencing
The BAC to BAC approach first creates a crude physical map of the whole genome before sequencing the DNA. Constructing a map requires cutting the chromosomes into large pieces and figuring out the order of these big chunks of DNA before taking a closer look and sequencing all the fragments.	The shotgun sequencing method goes straight to the job of decoding, bypassing the need for a physical map. Therefore, it is much faster.

Two approaches have been used to sequence the genome. They differ in the method they use to cut up the DNA, assemble it in the correct order and whether they map chromosomes before decoding the sequence. First, there was the BAC to BAC approach. A second newer method is called whole genome shotgun sequencing.

How does a degenerate code differ from an unambiguous one?

DEGENERATE	UNAMBIGUOUS
A single amino acid can be coded by more than one codon hence the genetic codon is called degenerate or reductant.	Each codon can only code for one amino acid and can not code for more amino acids, therefore, the genetic codon is called unambiguous.

Draw and label the secondary structure of tDNA carrying methionine.

1379613_1297345_ans_340b6432dece458fa2b32d665eea2a0c.jpg

The twisted ladder like structure of a double stranded DNA is also called ?

DNA is also called a three-dimensional double helix. It looks much like a twisted ladder, and the backbone of the ladder is made of sugar phosphates. The sugar in DNA -- deoxyribose -- is where the name deoxyribonucleic acid comes from. Deoxyribose is a modified form of the sugar ribose, which is the sugar that RNA is made of. The DNA ladder rungs are made from four organic bases, called cytosine, thymine, adenine, and guanine. Biologists shorten these terms to C, T, A, and G. Each rung contains two organic bases, but A can only pair with T, while C can only pair with G.

Where codons and anticodons are present?

Codons are present on an mRNA or DNA. They are sequences of three nucleotides that code for a specific amino acid. Anticodons are present on the tRNA (transfer RNA) molecules that help transfer or bring in the amino acids to the mRNA during the translation process. An anticodon also contains a three nucleotide sequence. The nucleotides are complementary to the sequence of nucleotides present on the mRNA being translated, such that the anticodon in the tRNA can interact with the specific codon in the mRNA and thereby bring the specific amino acid being coded for by the mRNA during the translation process.
1092380_1225051_ans_8a32b16c83bd4eea86fa943e651b752d.jpg

1092380_1225051_ans_8a32b16c83bd4eea86fa943e651b752d.jpg

Summarize the action of the gene introduced.

Cry I Ab/ Bt toxin gene codes for crystal protein; the Bt toxin protein exists as an inactive protein, but once an insect ingests it, it gets converted into an active form due to the alkaline pH of the gut which solubilizes the crystal. The activated toxin binds to the surface of mid gut and creates pores that cause swelling, lysis and eventually death of the insect.

What is DNA Fingerprinting?

DNA profiling (also called DNA fingerprinting) is the process of determining an individual's DNA characteristics, which are as unique as fingerprints. DNA analysis intended to identify a species, rather than an individual, is called DNA barcoding.

Draw a labelled diagram of t-RNA-the adapter molecule.

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The proportion of nucleotides in a given acid are : adenine 18%, Guanine 30%, Cytosine42 % and Uracil 10 %. Name the nucleic acid and mention the number of strands in it.

It is a ribonucleic acid (RNA) because it contains uracil. Uracil is present only in the RNA.
As the nucleic acid is RNA, then it will be single-stranded. Unlike double-stranded DNA, RNA is a single-stranded molecule in many of its biological roles and consists of a much shorter chain of nucleotides.
Hence, the nucleic acid is RNA and it is single-stranded.

What are the components of a transcription unit?

The process of copying genetic information from antisense or template strand of the DNA into RNA is called transcription.
The segment of DNA that takes part in transcription is called transcription unit. It has three components - A promoter, the structural gene and a terminator.
A promoter is a region of DNA that initiates transcription of a particular gene. Promoters are located near the transcription start sites of genes on the same strand and upstream on the DNA.
A structural gene is a gene that codes for an RNA or protein product other than a regulatory factor (i.e. regulatory protein). It may code for a structural protein, an enzyme, or an RNA molecule not involved in regulation.
A terminator is a sequence of DNA that causes RNA polymerase to terminate transcription.

What are the components of a nucleotide?

Nucleotides are organic molecules that serve as the monomer units for the formation of nucleic acid polymers such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth.
Nucleotides are the building blocks of nucleic acids. They are composed of three subunit molecules: a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and at least one phosphate group.
Nitrogenous base - Purines or pyrimidines such as Adenine, Guanine, Cytosine, Thymine or Uracil.
Sugar - Either ribose sugar or deoxyribose sugar.
Phosphate group - 1 phosphorus atom joined to 4 oxygen atoms

What is transcription?

$$\bullet$$ Transcription is the process of synthesizing RNA by copying genetic information from one strand of DNA.

$$\bullet$$ Transcription can be carried out by different enzymes such as RNA polymerase as well as multiple accessory proteins.

What is Human genome project ? Briefly write about the salient features of Human Genome project.

The Human Genome Project was an international scientific research project with the goal of determining the sequence of nucleotide base pairs that make up human DNA, and of identifying and mapping all of the genes of the human genome from both a physical and a functional standpoint. Human Genome Project had many goals some of the important goals were outlined below:

1. To identify all the approximately 20,000-25,000 genes in human DNA.

2. To determine the sequences of the 3 billion base pairs that make up human DNA.

3. To store this information in the database.

4. To develop improvised tools for data analysis.

5. To transfer related technologies to other sectors, such as industries.

6. To address the ethical, legal and social issues (ELSI) that may arise from the project.

Stae the importance of a Genetic code in protein biosynthesis.

One codon codes for only one amino acid, hence it is unambiguous and specific.

Example - AUG codes for Methionine.

The genetic code is a set of rules by which information encoded in genetic material (DNA or RNA) is translated to proteins. The code is universal and the triplet codon codes for the specific amino acid and these amino acids together forms the protein which regulate various processes in our body.

Write the contribution of the following scientists in deciphering the genetic code.
Georce Gamow; Hargobind Khorana; Marshall Nirenberg; Severo Ochoa

George Gamow - He suggested that in order to code for all the amino acids, the code should be made up of three nucleotides.

Hargobind Khurana - He developed the chemical method which was instrumental in synthesizing RNA molecules with a defined combination of bases (homopolymers and copolymers)

Marshall Nirenberg - His cell-free system for protein synthesis finally helped the code to be deciphered.

Severo Ochoa - Severo Ochoa enzymes (polynucleotide phosphorylase) was helpful in polymerizing RNA with defined sequences in a template-independent manner. (enzymatic synthesis of RNA)

Answer the following question in your own word.

Express your opinion about the use of DNA fingerprinting.

DNA fingerprinting is a method for comparing the DNA sequences of any two individuals. 99.9% of the base sequences in all human beings are identical. It is the remaining 0.1% that makes every individual unique.
The applications of DNA fingerprinting are as follows:
$$\bullet$$ DNA fingerprinting is widely used in forensics since the DNA of every tissue from an individual has the same degree of polymorphism.
$$\bullet$$ DNA fingerprinting forms the basis of paternity testing since a child inherits polymorphism from both its parents.
$$\bullet$$ It can be used for studying evolution and genetic diversity in a population.

List any four major goals of Human Genome project.

Human genome project was discovered by Francis Collins and Roderick.

(i) Human genome project aims at determining the complete and accurate sequence of 3 billion nucleotide that makes the whole human DNA.

(ii) It aims to find out all estimated, 20000 to 25000 genes, in human.

(iii) It also aims at sequencing entire genome of several organisms which are important in medical research.

(iv) Identification of disease-causing genes and their elimination.

(v) To introduce new genes that code for desired protein products.

What is the genomic library?

The collection of the cloned segments of the entire genome of any organism is called the genomic library. A genomic library is formed by taking out the complete DNA content of the haploid set of chromosomes of an organism.

What background information did Watson and Crick have made available for developing a model of DNA? What was their contribution?

Watson and Crick made following background Information available for developing a model of DNA:
$$*$$ Pairing between the two strands of polynucleotide chains.
$$*$$ Base pairing of polynucleotide chains is complementary in nature.
$$*$$ If base sequence of one strand is known, then the base sequence of another strand can be predicted.
$$*$$ If each strand from a DNA acts as a template. then both the daughter DNAs would be similar to the mother DNA.

Contributions of Watson and Crick:
$$*$$ A simple model of DNA was available because of them.
$$*$$ Genetic implications of DNA replication could be easily understood.
$$*$$ The model brought revolution in understanding of biology at a molecular level.

Explain the process of forming the Genomic Library.

The collection of the complete DNA content of a haploid set of chromosomes (genome) of an organism is called its genomic library. A genomic library is formed by isolating entire DNA from a cell. The genomic library is formed by the following method:
1864815_1873180_ans_fe4834c830ba4e708b01663d0b1ae88e.jpg

1864815_1873180_ans_fe4834c830ba4e708b01663d0b1ae88e.jpg

How has the sequencing of human genome opened new windows for treatment of various genetic disorders. Discuss amongst your classmates.

Sequencing of human genome has opened new windows for treatment of various genetic disorders. We know that genetic disorders are caused by some alteration in genes At present, we do not have exact information about the base pair sequence where this alteration takes place. Hence, we are unable to devise any tool to prevent genetic disorders. By proper understanding of the particular sequence responsible for a particular genetic disorder, the scientist may be able to devise some tools to prevent genetic disorders. A future may come when nobody will be suffering from genetic disorders; especially those which create serious disability.

List the various markers that are used in DNA finger printing.

A DNA marker is a gene sequence on a known chromosome that can be used to identify an individual or a species. A genetic marker or DNA marker can be a short sequence or a long sequence. The following are the commonly used markers for DNA fingerprinting.
$$*$$ RFLP (Restriction fragment length polymorphism)
$$*$$ SSLP (Simple sequence length polymorphism)
$$*$$ AFLP (Amplified fragment length polymorphism)
$$*$$ RAPD (Random amplification of polymorphic DNA)
$$*$$ VNTR (Variable number tandem repeat)
$$*$$ SSR Microsatelllte polymorphism, (Simple sequence repeat)
$$*$$ SNP (Single nucleotide polymorphism)
$$*$$ STR (Short tandem repeat)
$$*$$ SFP (Single feature polymorphism)
$$*$$ DArT (Diversity Arrays Technology)
$$*$$ RAD markers (Restriction site associated DNA markers)

Who revealed biochemical nature of the transforming principle? Now was it done?

Oswald Avery, Colin MacLeod and Maclyn McCarty (1933 - 1944) conducted experiments to reveal the biochemical nature of the transforming principle. They purified biochemical (proteins, DNA and RNA) form the heat-killed S cells. They wanted to see which one of them was able to transform the R strain. So, they discovered that protein-digesting enzymes (proteases) and RNA-digesting enzymes (RNases) did not affect transformation but DNase inhibits transformation. Thus, they concluded that it was the DNA that was able to transform the R strain.

Based on your understanding of genetic code, explain the formation of any abnormal hemoglobin molecule. What are the known consequences of such a change?

Normally human beings have following types of hemoglobin, $$Hb^A, Hb^{A2}$$ and $$Hb^F$$. Alteration in genes for beta chain on hemoglobin results in formation of $$Hb^S$$ type of hemoglobin. This type of hemoglobin molecule is responsible for Wide cell anemia,

Give any six features of the human genome.

Six features of the human genome are as follows:

$$*$$ The human genome contains 3164.7 million nucleotides.

$$*$$ The average gene in the human genome contains 3000 bases.

$$*$$ The total number of genes is estimated to be 30,000.

$$*$$ Almost all (about 99.9%) of nucleotides are same in all human beings.

$$*$$ Less than 2 percent of the genome codes for protein.

$$*$$ Chromosome 1 has the most genes (2969) and chromosome Y has the least (231).

The enzyme DNA polymerase in E.coli is a DNA dependent polymerase and also has the ability to proof-read the DNA strand being synthesised. Explain. Discuss the dual polymerase.

DNA polymerase uses DNA template to catalyse the polymerization of deoxynucleotides and hence it is called DNA - dependent. When a new strand of DNA is being processed, this enzyme moves along to hasten the speed of polymerization. While doing so, it "proof reads" the strand being formed. By doing so, it helps In speeding up the process. Hence, its nature can be said as dual, i.e. of reading the template and then proof reading the new strand.

Give an account of the methods used in sequencing the human genome.

Two approaches were involved in sequencing the Human genome.
Using Expressed Sequence Tags (ESTs): In this approach, all the genes that are expressed as RNA are identified and then sequenced.
Blind Approach: This approach involved sequencing the whole set of genome and then assigning different regions in the sequence with functions. This is referred to as sequence annotation. This approach Is comprised of following steps:
$$*$$ Total DNA from a cell is isolated and converted into random fragments of smaller sizes.
$$*$$ These fragments are cloned in a suitable host by using specialized vectors. The cloning results Into amplification of each fragment, and makes it easy to sequence the fragment Bacteria and yeast are the commonly used hosts for this purpose. The vectors were called as BAC (bacterial artificial chromosomes) and YAC (yeast artificial chromosomes).
$$*$$ Automated DNA sequencers were used to sequence the fragments. Then these sequences were arranged on the basis of some overlapping regions present in them.
$$*$$ For generating overlapping fragments in these sequences; help of computer programmes was taken because It was not possible for humans to do so.
$$*$$ Then the sequences were annotated and assigned to each chromosome.
$$*$$ Genetic physical mapping of genome was done on the basis of polymorphism in some segments of the DNA.

What 3 codons act as termination signals?

In the standard genetic code, there are three termination codons i.e. amber, ochre, and opal. The stop codons are UAG (amber), UAA (ochre), and UGA (opal).

What is the role of the helicase enzyme in DNA replication ?

DNA is double-stranded. Enzymes that are responsible for the replication of DNA (DNA dependent DNA polymerase) can only bind to a single strand of DNA. Helicase is the enzyme that unwinds the DNA by breaking hydrogen bonds between the two strands and forms a replication fork.

What is meant by triplet codon ?

$$\bullet$$ The triplet codon is the sequence of three nucleotides present in DNA or RNA molecule.

$$\bullet$$ The triplet codon forms amino acids after translation.

$$\bullet$$ The triplet consists of combinations of four nucleotide bases as adenine, guanine, cytosine, uracil and thymine.

$$\bullet$$ For example: A U G code for methionine amino acid.

How is "DNA fingerprinting" done?

The first step is isolating the desired DNA which can be performed chemically, mechanically, or enzymatically.

The second step is cutting the DNA into several pieces by restriction enzymes.

The third step is sorting the DNA pieces by gel electrophoresis. The DNA will be separated by size.

The next step is denaturing the DNA fragments.

The next step is the Southern blot. The gel with the size-fractionated DNA is applied to a sheet of nitrocellulose paper or nylon membrane.

In order to analyze a Southern Blot, a radioactive genetic probe is used in a hybridization reaction with the DNA. The X-ray film helps to analyze the fragments.

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How is the polymerase chain reaction useful in DNA fingerprinting?

DNA fingerprinting is also called DNA profiling. It is a laboratory technique used to identify individuals with the characteristics of their DNA. It is used to solve some crime mysteries like murder, rape, etc. Usually, the samples (e.g., blood, semen, saliva) that are available for the testing are small. Hence, a polymerase chain reaction is used to amplify the amount of DNA present in the sample.

How is "DNA fingerprinting" done?

The steps in the DNA fingerprinting are:

Isolation of the DNA.
The DNA is fragmented using the restriction enzyme.
Separation of the DNA fragments by electrophoresis.
Transferring of the DNA to synthetic membrane.
Addition of the complementary probes and hybridization.
Detection of the hybrid DNA fragments by autoradiography.

What are the rungs of the DNA ladder made up of?

The rungs of the DNA ladder made of four types of nitrogenous bases. These are adenine (A), guanine (G), cytosine (C), and thymine (T). These nitrogen bases pair as A-T and C-G with the help of two and three hydrogen bonds respectively.

Match the names of the scientists with their contributions and choose the correct answer.
Column I - Name of scientists
Column II - Contributions

Walter Sutton a scientist who discovered that mendelian theory can be applied to chromosomes.

Stanley cohen developed rDNA

Alexander Flemming discovered the antibiotic penicillin.

Watson along with crick discovered the double helical structure of DNA

Identify the correct match between the codons and coding functions.
A) A-2, B-3, C-4, D-1
B) A-1, B-2, C-3, D-4
C) A-4, B-3, C-2, D-1
D) A-3, B-2, C-4, D-1

Codon 'AUG' codes for methionine. 'UAA' is a stop codon/termination codon which means that it does not code for any amino acid. Triplet 'UUU' codes for phenylalanine and 'UGG' codes for tryptophan.

Define a gene?

Genes are the specific parts of a chromosome (DNA segment) which determine the hereditary characteristics.

Match the following in column I with column II and choose the correct combination.

DNA replication is the synthesis of DNA strands using parental DNA as the template by enzyme DNA polymerase. Lagging DNA strand is synthesized in the 5'-->3' direction by adding a new primer every few hundred bases on the second parental strand. Each of these primers is elongated in the 5'-->3' direction and form discontinuous segments called as Okazaki fragments.

Transcription is the process of RNA synthesis using DNA template strand. RNA polymerase adds ribonucleotides to 3’ end of primer and chain grows in 5’ to 3’ direction.

The first stage of translation takes place in the cytosol where aminoacyl-tRNA synthetases esterify the 20 amino acids to their corresponding tRNAs.

The carboxyl group of the amino acid reacts with the $$\alpha$$-phosphoryl group of ATP to form an enzyme-bound intermediate, aminoacyl adenylate, followed by transfer of aminoacyl group from enzyme-bound aminoacyl-AMP to its corresponding specific tRNA.

Three GTP-dependent termination factors, or release factors namely RF-1, RF-2, and RF-3 terminate the translation by hydrolysis of the terminal peptidyl-tRNA bond to release free polypeptide and last tRNA from the P site followed by dissociation of the 70S ribosome into its 30S and 50S subunits.

Draw a schematic diagram of a part of double stranded dinucleotide DNA chain having all the four nitrogenous bases and showing the correct polarity.

(a) A DNA segment has a total of 1,500 nucleotides, out of which 410 are guanine containing nucleotides. How many pyrimidine bases this segment possesses?
(b) Draw a diagrammatic sketch of a portion of DNA segment to support your answer.

Adenine an Guanine are purines while cytosine and thymine are pyrimidines.

According to Chargaff's rule, the ratio of purines to pyrimidines is equal.

Thus, the number of cytosine (C) will be equal to the number of guanine (G).

As it is given that the number of guanine-containing nucleotides = 410

Thus, G = C = 410

Now, G + C = 410 + 410 = 820

The number of adenine (A) will be equal to the number of thymine (T).

Thus, A + T = Total number of nucleotides – Nucleotides containing G and C nitrogenous bases

= 1500 – 820 = 680

Therefore, A = 340 and T = 340

The number of adenine will be equal to number of thymine, which is 340.

Therefore, Number of pyrimidines that the segment possess = C + T

= 410 + 340 = 750

(a) Write the specific features of the genetic code AUG.
(b) Genetic codes can be universal and degenerative. Write about them, giving one example of each.
(c) Explain aminoacylation of tRNA.

(a) AUG codes for methionine and is the initiator codon.

(b) Some amino acids are coded by more than one codon and hence the code is degenerate. For example, phenylalanine or Phe is coded by UUU as well as by UUC.

The code in nearly universal, meaning, from micro-organism to human beings, the codon would code for the same amino acid. For example, UUU would code for Phe from bacteria to human (though some exceptions are found in mitochondrial codons and in some protozoans).

(c) Aminoacylation of tRNA is the first phase of translation where amino acids are activated in the presence of ATP and linked to their cognate tRNA. An aminoacyl tRNA synthetase is an enzyme that attaches the appropriate amino acid onto its tRNA. Enzyme and AMP are released. tRNA complexed with an amino acid is sometimes called charged tRNA. The amino acid is linked to 3'-OH end of tRNA through its -COOH group.

AA-AMP + t + tRNA --> AA-tRNA + AMP + Enzyme

What do '$$Y$$' and '$$B$$' stand for in '$$YAC$$' and '$$BAC$$' used in Human Genome Project (HGP)? Mention their role in the project.

YAC stands for Yeast Artificial Chromosome and BAC stands for Bacterial artificial chromosome.

YAC are derived from DNA of yeast S. cerevisiae by the process of genetic engineering. They are then ligated into the bacterial plasmid. By inserting large fragments of DNA, the inserted sequences can be cloned and mapped by chromosome walking and this method was used in the Human Genome Project.

BAC is a DNA construct used for transforming and cloning in bacteria like E. coli. They are used to sequence the genome of an organism in genome projects.

Following are the features of genetic codes. What does each one indicate? __________ Stop codon, Unambiguous codon, Degenerate codon, Universal codon.

Answer:

Characteristics of the genetic code:

Stop codon: Signals the end of translation but does not encode any amino acids. UAA, UAG, UGA - these are the termination codons.
Unambiguous codon: Each codon just codes for one amino acid.
A degenerate codon : More than one codon can code for a specific amino acid.
Universal codon: In all species, one codon codes for the same amino acid.

Write the percentage of the total human genome that codes for proteins and the percentage of discovered genes whose functions are known as observed during HGP.

Genes whose functions are known as protein-coding sequences and they comprise less than 2 percent of the human genome.

Expand 'SNPs' identified by scientists in HGP.

$$\textbf{Solution:}$$

$$\bullet$$ Single nucleotide polymorphisms is frequently called SNPs are the most common type of genetic variation that occur among people.

$$\bullet$$ Each SNP represents a difference in a single DNA building block, called a nucleotide.

$$\bullet$$ Most commonly, these variations are mostly found in the DNA between genes.

$$\bullet$$ SNPs in the coding region are of two types: synonymous and non-synonymous SNPs. Synonymous SNPs have no affect on the protein sequence, while non-synonymous SNPs change the amino acid sequence of protein.

$$\bullet$$ SNPs are single nucleotide polymorphism that occur at about 1.4 million locations in human DNA.

Give any two features of genetic code.

The genetic code is non-overlapping or non-ambiguous. Each nucleotide is a part of only one codon and is read only once during translation.

The genetic code is almost universal. In nearly all organisms, most codons code for the same amino acid. This avoids confusion in reading the codes and determining the amino acid.

What does abbreviation HGP stand for ?

HGP is the abbreviation which stands for Human Genome Project which was performed to determine the total number of genes in the genome of human being.

Sketch and label hair-pin model of $$t$$-RNA.

What are introns?

The DNA have regions called as exons and introns. Introns are the regions which do not code for the proteins. These are the regions which are removed from the mRNA by the splicing process. The exons are the regions which encode for the amino acids in the proteins. The introns are removed and the exons are ligated during post transcriptional modification.

Give diagrammatic representation to show a perfect pairing and any two wobble pairings.

The genetic code is degenerate, as 61 codons are available for 20 amino acids. Two or more codons can specify the same amino acid. In 1966, Crick proposed Wobble hypothesis to explain this. This hypothesis explains that in codon-anticodon pairing, the third base may not be complementary. The third base of the codon is called wobble base and this position is called wobble position. The actual base pairing occurs at first two positions only. For example, GUU, GUC, GUA and GUG code for amino acid Valine.

What will be the length of eukaryotic DNA segment having 10 pairs of nucleotides?

The type of DNA in the eukaryotes is the B-DNA. In the B-DNA, the distnace between base pairs is 3.4 A$$^o$$. There are 10 base pairs in one turn of helix. The length of the helix is 3.4 x 10 = 34 A$$^o$$. The length of the DNA segment having 10 bases will be 34 A$$^o$$.

State any three goals of the human genome project.

The Human Genome Project (HGP) is an international research program that is to spell out the complete genetic inheritance of human beings and selected experimental animals. The HGP's goal is to decode the complete DNA inheritance, or genome of human beings by 2003 and make them accessible for further biological study. The Department of Energy's Human Genome Program and the National Institutes of Health's National Human Genome Research Institute (NHGRI) together sponsored the U.S Human Genome Project.
Objectives or goals of Human Genome Project (HGP) are:
(i) To develop new and improved medicines.
(ii) To predict and prevent diseases.
(iii) To ensure that the diagnosis is accurate.
(iv) To improve forensic science.

Write four goals of Human Genome project

Human genome project was discovered by Francis Collins and Roderick.

(i) Human genome project aims at determining the complete and accurate sequence of 3 billion nucleotide that makes the whole human DNA.

(ii) It aims to find out all estimated, 20000 to 25000 genes, in human.

(iii) It also aims at sequencing entire genome of several organisms which are important in medical research.

(iv) Identification of disease-causing genes and their elimination.

(v) To introduce new genes that code for desired protein products.

In a typical DNA molecule, the proportion of thymine is 30% of the N bases. Find out the percentages of other N bases.

According to the rule given by Chargaff, A + G = C + T.

Adenine (A) will always pair with Thymine (T). This means that A = T.

Cytosine (C) will always pair with Guanine (G). This means that C = G.

Since the proportion of thymine T = 30%, so, A = 30%.

G + C = 100 - 60% = 40%

So, G = 20% and C = 20%.

Therefore, the answer is T = 30%, A = 30%, G = 20% and C = 20%.

What is Human Genome project? Write the salient features of Human genome project. Draw a representative diagram of Human genome project.

The Human Genome Project is an international research project with the goal of determining the sequence of human DNA and of identifying it,

Salient features of Human genome project:

(i) U.S. Department of Energy and National Institute of Health embarked and coordinated on the project of sequencing human genome called HGP or Human Genome Project.

(ii) HGP is a mega project involving a lot of money, most advanced techniques, numerous computers and scientists at work.

(iii) HGP was closely associated with rapid development of a new era in biology called as Bioinformatics.

Describe the characteristics of genetic code?

a) Commaless: Genetic code is commaless. This means that the arrangement of triplet codons on m-RNA is one after other without a gap.

b) Non-ambiguous nature: Each codon specifies a particular amino acid. The only exception is AUG which codes for methionine and GUG and codes for valine. But in the absence of AUG, GUG can also code methionine.

c) Degenerate nature: There are 61 codons for 20 amino acids. But some amino acids are coded by more than one codon. Hence it is said to be degenerated. e.g. GGG, GGA, GGC and GGU all code for glycine.

d) Polarity: Genetic code could be read only in 5'-3'direction on m-RNA. This polarity is the important aspect of the genetic code.It also has start and stop signals. Start or initiation codon is AUG while UAG, UAA, UGA are the stop or termination codes.

e) Universality: Genetic code is universal for all the organisms from simple bacteria to complex organisms.

Write any four salient features of the Double helix structure of DNA.

The salient features of double helix structure of DNA are as follows:

There are two polynucleotide chains in a double stranded DNA.
The backbone is constituted by sugar phosphate.
The two strands possess anti-parallel polarity, means one chain has polarity 5’-3’ and the other has 3’-5’.
The two strands of DNA are joined together by hydrogen bonds between purines and pyrimidines.
Adenine always pairs with Thymine by two hydrogen bonds and Guanine always pairs with Cytosine by three hydrogen bonds.
The two chains are coiled around each other where the pitch of the helix is 3.4 nm and distance between two base pairs is 3.4 A° (as in case of B-DNA)
The backbone of DNA double helix is formed by sugars and phosphates where bases are projecting inwards.

Who discovered the phenomenon of transformation in bacteria and in which year?

Frederick Griffith, in 1928.

Fill in the blanks with appropriate words.
If the sequences of bases in a segment of a DNA strand were adenine, thymine, cytosine, guanine, then the sequence in a complementary strand of newly made mRNA would be ..........

uracil, adenine, guanine, cytosine

In the light of Watson and Cricks model, describe the detailed structure of DNA.

Watson and Crick proposed that the DNA is a double-stranded structure. These are twisted around each other to form a right-handed helix, called a double helix.
Base-pairing occurs between a purine and pyrimidine: namely, A pairs with T and G pairs with C as adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs of each other.
Adenine and thymine are connected by two hydrogen bonds.
Cytosine and guanine are connected by three hydrogen bonds.
The two strands are anti-parallel in nature.
The diameter of the DNA double helix is uniform throughout because a purine (two rings) always pairs with a pyrimidine (one ring).
Their combined lengths are always equal.
Also according to the chargaff's rule purines and pyrimidines exist in the ratio 1:1.
The backbone of DNA is formed by alternating sugar and phosphate residues.

What is transcription? What are the different parts of a DNA transcription unit? What is their role in the process of transcription?

Transcription is the first step of gene expression. Using the DNA as a template, a piece of mRNA is made from the gene to be used by the enzyme RNA polymerase. This process is called transcription. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript.

Transcription Unit: The segment of DNA that takes part in transcription is called transcription unit. It has three components (i) a promoter, (ii) the structural gene and (iii) a terminator. Eukaryotes also require an enhancer.

(i) Promoter- It is located upstream of the structural gene. By convention, it is called 5′ end (of coding strand which is 3′ end of template strand). It has different parts for attachment to various transcription factors.

(ii) Structural gene- It is a component of that strand of DNA which has 3′→ 5′ polarity. This strand of DNA is called template strand or master strand or antisense, or (-) strand. The other strand which has a polarity of 5′→ 3′ is displaced during transcription. This non-template strand which does not take part in transcription is also called sense or coding strand or plus (+) strand because genetic code present in this strand is similar to genetic code (based on mRNA) except that uracil is replaced by thymine.

(iii) Terminator- This region is present downstream of the structural gene at the 3′ end (of coding strand which is actually 5′ end of the template strand).

Mechanism of Transcription: Transcription is divided into initiation, promoter escape, elongation, and termination. Because the code is buried within the DNA molecule, the first step is to open up the helix to expose the bases. Only the gene to be transcribed is opened, the remainder of the chromosome remains coiled. Opening up the helix exposes both base strands, but the enzyme that makes the mRNA uses only one of them. Hence, the mRNA molecule is single, not double-stranded. As the enzyme moves along the opened DNA strand, reading its code, it adds the complementary base to the mRNA. Therefore, if the DNA base is cytosine, guanine is added to the mRNA molecule (and vice versa); if it is thymine, adenine is added; if it is adenine, uracil is added. When the enzyme gets to a 'stop' signal, it terminates synthesis of the mRNA molecule, and the mRNA is released. The DNA is zipped up again by other enzymes, and the mRNA then leaves the nucleus.

Write a short note on DNA fingerprinting

DNA fingerprinting is a technique used to identify and analyze the variations in various individuals at the level of DNA. DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA because, in these sequences, a small stretch of DNA is repeated many times. These repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation. The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA. Depending on base composition (A:T rich or G:C rich), length of the segment, and the number of repetitive units, the satellite DNA is classified into many categories, such as micro-satellites, mini-satellites etc. These sequences normally do not code for any proteins, but they form a large portion of the human genome. These sequences show the high degree of polymorphism and form the basis of DNA fingerprinting. Since DNA from every tissue (such as blood, hair-follicle, skin, bone, saliva, sperm etc.), from an individual, show the same degree of polymorphism, they become very useful identification tool in forensic applications. Further, as the polymorphisms are inheritable from parents to children, DNA fingerprinting is the basis of paternity testing, in case of disputes.

Write a brief account of the contributions made by J. D. Watson, F.H.C. Crick and M.H.F. Wilkins.

Watson and Crick

- gave the double helical structure of DNA

- proposed a scheme of replication of DNA

Wilkins

- Along with Rosalind Franklin produced X-diffractions of DNA which led to the deduction of 3-D DNA structure by Watson and Crick

- discovered DNA is shaped like a twisted ladder

What is DNA fingerprinting? Why is it called finger printing?

DNA fingerprinting is the process of determining an individual's DNA characteristics, which are as unique as fingerprints. DNA fingerprinting is a technique that simultaneously detects lots of minisatellites in the genome to produce a pattern unique to an individual. It was developed by a British geneticist Prof. Alec Jefferys in 1984. The probability of having two people with the same DNA fingerprint that are not identical twins is very small. Each of us is genetically unique and this genetic variation could be used to identify individuals, as a conventional fingerprint does. Thus it is called DNA fingerprinting.

Write about the transfer RNAs as follows :
(a) Any two characteristics in their structure. (b) Part of the cell where they are located.
(c) The technical name for the set of bases that are complementary to the triplet code on the mRNA.

The transfer RNA is a family of about 60 small sized ribonucleic acids which can recognise the codon of mRNA and exhibit high-affinity for 20 activated amino acid.

tRNA molecule the smallest containing 70-80 nucleotides. The 3' end of the chain represents the site for attachment of activated amino acid. The end of the chain terminates with guanine base. The bent chain of each tRNA molecule contains a definite sequence of three nitrogenous bases which constitutes the anticodon. It recognises the codon sequence on mNA.

The tRNA is found in the cytoplasm of the cell why the translation takes place.

Short /Long answer type questions.
State any three goals of the human genome project.

$$\textbf{Solution}$$

$$\bullet$$ The Human Genome Project is a research based project whose goal is to determine the base pairs that makes up the human DNA.

$$\bullet$$ Three important goals of human Genome Project are:

$$\bullet$$ To determine the sequence of 3 billion base pair which makes up the human DNA.

$$\bullet$$ To identify all the genes that are present in the human DNA in an estimated value.

$$\bullet$$ To identify and sequence all the genes from both physical as well as functional point of view.

$$\bullet$$ To store all the information that we gain in a database.

$$\bullet$$ Human Genome Project is very important because this project the scientists are gaining information from the DNA in order to develop different ways to treat and cure thousands of disease which are affecting the humans.

Very short answer type.
What is a gene bank?

A gene bank is an institution where valuable plant material likely to become irretrivably lost in the wild or in cultivation is preserved in a viable condition. Gene banks conserve stocks of both seeds and vegetative material.

Wilkins familiarized the results of high resolution X-ray photographs of crystallized DNA obtained by Franklin to Watson and Crick. What values were shown by him?

Franklin's high resolution photographs of crystallised fibre of DNA and their elaborations of Wilkins helped Watson and Crick to correctly arrange the nucleotides and decide that DNA is a double stranded with two chains running in antiparallel fashion. Such a model had an inbuilt property of semiconservative replication.
The values shown by Wilkin were of high calibre. He not only explained the discovery before its publication but also helped Watson and Crick in one of the biggest development in biology that has direct impact on human welfare and welfare of the whole biological world.

Scientists have identified about 1.4 million single nucleotide polymorphs in human genome. How is the information of their existence going to help the scientists?

A more detailed map would also help scientists study complex human diseases and traits that involve many genes—for example, cancer, heart disease, and personality. In addition to helping in the search for genes, genome maps are useful in the day-to-day activities of molecular biology laboratories.

Name the enzyme involve in the continuous replication of DNA strand. Mention the polarity of the template strand.

DNA polymerase is an enzyme that synthesizes DNA molecules from deoxyribonucleotides, the building blocks of DNA. These enzymes are essential for DNA replication and usually work in pairs to create two identical DNA strands from a single original DNA molecule. Template strand is the strand which is used by DNA polymerase for replication process its polarity is always from 3 prime to 5 prime direction.

Write the function of RNA polymerase II.

RNA polymerase II (RNAP II and Pol II) is a multiprotein complex. It is one of the three RNAP enzymes found in the nucleus of eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. The main function of DNA polymerase is to make DNA from nucleotides, the building blocks of DNA. There are several forms of DNA polymerase that play a role in DNA replication and they usually work in pairs to copy one molecule of double-stranded DNA into two new double-stranded DNA molecules.

Fill the columns and complete the given table. Give explanation for your answer
Term Definition Example Complementary process/Example
1 Transcription ...... mRNA Translation
2 ...... Group of organisms that produces fetile individuals Tiger ....
3 Acquired Characters change in organs/body due to use-disuse during organism's life time .... Ancestry of acquired characters
4 Morphological Similiarities seen in animals ..... Leaf shape

Term	Definition	Example	Complementary process/Example.
1. Transcription	formation of mRNA from DNA template is called transcription	mRNA	Translation
2.Evolution	Group of organisms that produces fertile individuals	Tiger	Evolution
3.Acquired characters	Change in organs/ body due to use during organism’s life time.	Darwinism	Ancestry of acquired characters.
4.Morphological	Similarities seen in animals	Adaptations	Leaves

Explain the double helix structure of DNA with a labelled diagram.

DNA has a double-stranded helical structure.
It was given by Watson and Crick model.
It is also known as B form of DNA.
It is made up of nitrogenous base, deoxyribose sugar, and phosphate.
The nitrogenous base, deoxyribose sugar, and phosphate link together forms the nucleotide chain.
The two nucleotide chain is arranged as stacks connected by phosphate.
The phosphate connects the 3' carbon atom of one sugar molecule and the 5' carbon atom of another deoxyribose sugar of next nucleotide chain by phosphodiester bonds.
3'-5' linkage by phosphodiester bonds makes the two strands as antiparallel strands.
Nitrogenous base is of two types purines and pyrimidines.
Adenine and guanine is purines, while thymine and cytosine is pyrimidines.
Purines are linked to pyrimidines by hydrogen bonds.
The adenine and thymine is linked by two hydrogen bonds while cytosine and guanine is linked by three hydrogen bonds.
The nitrogenous bases are linked to the sugar by N-glycosidic bonds.
It has a diameter of 20 A$$^0$$.
The total helix runs to a length of 34A$$^0$$.
The axial rise per base pair is 3.4 A$$^0$$.
Base pair per turn is 10A$$^0$$.

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Explain the DNA fingerprinting method of forensic science.

The science of DNA sequencing has developed a lot since the first profiling was done by Sir Alec Jeffreys in 1985, in England. The entire genetic information of an individual is called genome. Genome contains the DNA sequence, which has both coding and non coding genes. The DNA sequences of humans are 99% similar in every individual. However, the other 1% is what makes each one of us unique. This 1% sequence mainly has specific codes that repeat itself throughout the sequence. These are short and varied sequences, and are known as VNTRs (Variable Number of Tandem Repeats). The frequency and position of these repeats vary greatly from one individual to the other. DNA fingerprinting uses such VNTRs from an unknown DNA sample to compare and match with the known.

Technique

The process is summarized below with a flowchart for better understanding:

What do you mean by semiconservative method of DNA? Who proved it and how?

Semiconservative replication describes the mechanism by which DNA is replicated in all known cells. It derives its name from the fact that this mechanism of transcription was one of three models originally proposed for DNA replication. The deciphering of the structure of DNA by Watson and Crick in 1953 suggested that each strand of the double helix would serve as a template for synthesis of a new strand. However, there was no way of knowing how the newly synthesized strands might combine with the template strands to form two double helical DNA molecules. The semiconservative model seemed most reasonable since it would allow each daughter strand to remain associated with its template strand. The semiconservative model was anticipated by Nikolai Koltsov, supported by the Meselson-Stahl experiment and other even more revealing experiments that allowed for autoradiographic visualization of the distribution of old and new strands within replicated chromosomes. The rate of semiconservative DNA replication in a living cell was first measured as the rate of phage T4 DNA strand elongation in phage-infected E. coli. During the period of exponential DNA increase at 37 °C, the rate of strand elongation was 749 nucleotides per second. The mutation rate per base pair per round of replication during phage T4 DNA synthesis is 2.4×10−8. Thus semiconservative DNA replication is both rapid and accurate.

Explain the structure of DNA.

DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C).
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Illustrate on Human Genome project (HGP) and the methods used for the study.

The HGP is a large effort to trace the genetic make up of genome of humans and other oragnisms. The complete architecture of human genome has been traced through studies during this project. HGP provides a detailed knowledge about the human DNA its composition , make up and the whole information to benefit biomedical field.
HGP involved two major approaches: Expressed Sequence Tags (ESTs) – This approach focussed on identifying all genes expressed as RNA. Sequence Annotation – This blind approach involved sequencing the whole genome (coding and non-coding) and later assigning functions to the different regions.

Define watson-crick model of DNA

The Watson crick model gives the structure of DNA as double standard helicase having to superphosphate backbone held together with a hydrogen bond between nitrogenous bases

What is degeneracy of genetic code?

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There is only one possible sequence of amino acids when deduced from a given nucleotides. But multiple nucleotides sequence can be deduced from a single amino acid sequence. Explain this phenomenon.

There are 61 codons and 20 amino adds. Hargobind Khorana and Marshall Neirenberg worked on this principle. It was proposed that a codon for an amino add is made up of 3 nucleotides. It was also seen that one codon codes for only one amino acid (unambiguous and specific). Some amino adds are coded by more than one codon (degeneracy of codon). In simple terms, It can be said that there Is only one possible sequence of amino adds when deduced from a given set of nucleotides. Rut multiple nucleotides sequence can he deduced from a single amino add sequence.

During in vitro synthesis of DNA, a researcher used 2', 3'- dideoxy cytidine triphosphate as raw nucleotide in place of 2'-deoxycytidine. What would be the consequence?

2', 3' - dideoxy cytidine triphosphate is a reverse transcriptase inhibitor. Reverse transcriptase is a viral DNA polymerase which facilitates DNA replication in HIV and other retroviruses. The commercial name of ddC is Zalcitabine and it is sold as a pharmaceutical product for management of HIV. If 2*, 3'- dideoxy cytidine triphosphate is used as a raw nucleotide in place of 2' - deoxycytidine, it will stop DNA replication. The researcher will not be able to proceed with his experiment because of contrary effect of his chosen reagent.

Name a few enzymes involved in DNA replication other than DNA polymerase and ligase. Name the key functions for each of them.

Following are some other enzymes and their key functions during DNA replication:

$$*$$ Primase: It adds RNA primers to template strands.

$$*$$ RNAse: Removes the RNA primer.

$$*$$ Exonuclease: Initiate cleaving or nucleotides one at a time.

Define transformations in Griffith's experiment. Discuss how it helps in the identification of DNA as the genetic material.

During the course of Griffith's experiment. bacteria changed Its physical form. This was termed as transformation. In this experiment, the DNA of the S strain bacteria survived heating of bacteria. When mice were injected with mixture of killed S strain and R strain, the mice died of pneumonia. This showed that DNA had the capability of surviving adverse circumstances and manifesting Itself on return of favourable conditions. Stability and survival are key considerations for a material to be classified as genetic material. Thus, transformation in Griffith's experiment helped in Identification on DNA as genetic material.

Would it be appropriate to use DNA probes such as VNTR in DNA finger printing of a bacteriophage?

VNTR (Variable Number Tandem Repeat) is a location in genome where a short nucleoside is organized as tandem repeat. Analysis of VNTR is used for many purposes; Including DNA fingerprinting. But bacteriophage does not have too many DNAs rather only a few strands of DNA are available in bacteriophage. This does not leave scope for repeating sequence in DNA. Hence, VNTR cannot be used in DNA fingerprinting of a bacteriophage.

Given below is one of the strands of a DNA segment :
$$3' \overset{TACGTACGTACGTACG}{\rightarrow} 5'$$
(a) Write its complementary strand.
(b) Write a possible RNA strand that can be transcribed from the above DNA molecule formed.

Answer-

A. Complementary DNA strand- 5' ATGCATGCATGCATGC 3'

B. RNA strand -5'UACGUACGUACGUACG-3'

Molecular Basis Of Inheritance - Class 12 Medical Biology - Extra Questions

What is the function of the codon AUG?

Differentiate between the genetic codes :Degenerate and Initiator

Protein sequences are encoded in ..........

Explain the following: Degenerate code, Unambiguous code, Universal code, Initiator code.

Match the names of triplet codons with the amino acids given under columns. Choose the answer which gives the correct combination of the alphabets of the two columns.(a) A- s, B- t, C- q, D- r(b) A- t, B- s, C- r, D- q(c) A- p, B- r, C- s, D- t(d) A- q, B- r, C- s, D- t

What is a genetic code?

Explain the significance of satellite DNA in DNA fingerprinting technique.

State the difference between the structural gene in a transcription unit of prokaryotes and eukaryotes.

Name the transcriptionally active region of chromatin in a nucleus.

(a) Construct a complete transcription unit with promoter and terminator on the basis of the hypothetical template strand given below:(b) Write the RNA strand transcribed from the above transcription unit along with its polarity.

Name the scientist who suggested that the genetic code should be made of a combination of three molecules.

What would be the molar concentration of human DNA in a human cell? Consult your teacher.

Name the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of a DNA molecule.

Why is the Human Genome project called a mega project?

Briefly describe the following:(a) Transcription(b) Polymorphism(c) Translation(d) Bioinformatics

Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.

Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.

Group the following as nitrogenous bases and nucleosides:Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

Collect $$5$$ examples of palindromic sequence by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.

What is complementary base pairing?

State the best known contribution of:(i) Alec Jeffery(ii) P.K. Sethi(iii) Hugo de Vries

With the help of a neat and labeled diagram describe Waston and Crick's model of DNA.

Describe Watson and Crick's model of DNA.

Sketch and label hair- pin model for t-RNA.

What is genetic code? Write its four salient features. Draw a diagram of t-RNA.

What is nucleosome ? Draw diagram of double stranded polynucleotide chain of DNA and explain its structure.

Draw a neat labelled diagram of the hair pin model of t-RNA?

Write down the four salient features of genetic code.

Give the application of DNA fingerprinting technique.

What is human genome project (HGP)?

Write the important features of genetic code.

What is DNA fingerprinting? Write any four applications of DNA fingerprinting.

What is DNA Library?

In a typical DNA molecule, the proportion of thymine is $$20\%$$ of the N bases. Find out the percentages of other N bases.

In a typical DNA molecule, the proportion of thymine is $$30$$% of the $$N$$ bases. Find out the percentage of other $$N$$ bases.

List the salient features of human genome project.

Define stop codon. Write the codons.

Explain 'Wobble hypothesis' with the help of a suitable diagram.

Answer in 200 to 250 words:Enumerate the salient features of Human Genome Project (HGP).

Describe the process of DNA replication with the help of a diagram.

Explain replication of bacteriophage with the help of a suitable diagram.

Newly formed DNA copies may not be identical at times. Gives one reason.

What is DNA replication? Write the chemical composition of DNA.

Differentiate between the genetic codes: Unambiguous and Universal

Rearrange B and C according to the data given in A. A B C Nucleic Acids Sugar Nitrogen BaseDNAa) Ribosomex) UracilRNAb) Deoxyribosey) Adeninec) Ribosez) Thymine

Diagrammatic representation of 'central dogma' is given below :Observe the diagram carefully and redraw it making appropriate corrections.$$\circlearrowleft DNA \xrightarrow [] {translation} mRNA \xrightarrow [] {transcription} Protein $$

Find the odd one. Write down the common features of others.Adenine, Cytosine, Thymine, Uracil.

List the two methodologies which were involved in human genome project. Mention how they were used.

Given below is the transcribed strand of the DNA duplex :3'-TACCGATCCGAGCTG-5'(a)Draw the complementary DNA polynucleotide chain(b)Construct the RNA molecule, which will'be transcribed.

Briefly discuss the structure and functions of DNA.

What do you understand by the antiparallel arrangement of DNA strands?

Match the triplet codons mentioned in list I with their amino acids mentioned in listcolumn II and select the correct option from the given codes.

'Genetic code is unambiguous and specific.' Explain.

The double helix model for DNA was proposed by .......... and ..........

Chemical analysis has shown that the number of adenine molecules in a DNA sample is always the same as the number of molecules of ..........

Very short answer type.Name two scientists who were awarded Nobel Prize for deciphering DNA structure.

Write the importance of DNA.

Double-helical structure is found in ..........

Differentiate between nucleoside and nucleotide.

What name is applied to the model for the molecular structure of DNA?

Why is the Human Genome Project called a mega project?

What is transformation?

Give reasons Genetic code is universal.

The genetic code is said to be a triplet code. What does this mean and why is it important?

How do a code, codon, and anticodon differ?

(a) Explain the experiment performed by Griffith on Streptococcus pneumoniae. What did he conclude from this experiment?(b) Name the three scientists who followed up Griffiths experiments.(c) What did they conclude and how?

(a) How many codons code for amino acids and how many do not?(b) Explain the following giving one example of each(i) Unambiguous and specific codon(ii) Degenerate codon(iii) Universal codon(iv) Initiator codon.

What is amplification with reference to DNA fingerprinting?

Describe the experiment performed by Griffith. What conclusions did he infer from his observations?

What is genetic code? Mention the essential qualities for a universal genetic code.

Why are there 64 different codons for 20 different amino acids?

Codon AUG has dual function. Justify.

List the salient features of human genome.

What is the diagram representing?

Mention the $$DNA$$ sequence coding for serine and the anticodon to $$tRNA$$ for the same amino acid.

Name the parts a, b and c.

Mention the contribution of genetic maps in human genome project.

How do histones acquire positive charge?

Give salient features of human genome.

Differentiate between the genetic codes :
Degenerate and Initiator

Match the names of triplet codons with the amino acids given under columns. Choose the answer which gives the correct combination of the alphabets of the two columns.
(a) A- s, B- t, C- q, D- r
(b) A- t, B- s, C- r, D- q
(c) A- p, B- r, C- s, D- t
(d) A- q, B- r, C- s, D- t

(a) Construct a complete transcription unit with promoter and terminator on the basis of the hypothetical template strand given below:
(b) Write the RNA strand transcribed from the above transcription unit along with its polarity.

Briefly describe the following:
(a) Transcription
(b) Polymorphism
(c) Translation
(d) Bioinformatics

Group the following as nitrogenous bases and nucleosides:
Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

State the best known contribution of:
(i) Alec Jeffery
(ii) P.K. Sethi
(iii) Hugo de Vries

Answer in 200 to 250 words:
Enumerate the salient features of Human Genome Project (HGP).

Differentiate between the genetic codes:
Unambiguous and Universal

Rearrange B and C according to the data given in A.
A B C
Nucleic Acids Sugar Nitrogen Base
DNA a) Ribosome x) Uracil
RNA b) Deoxyribose y) Adenine
c) Ribose z) Thymine

Diagrammatic representation of 'central dogma' is given below :
Observe the diagram carefully and redraw it making appropriate corrections.
$$\circlearrowleft DNA \xrightarrow [] {translation} mRNA \xrightarrow [] {transcription} Protein $$

Find the odd one. Write down the common features of others.

Adenine, Cytosine, Thymine, Uracil.

Given below is the transcribed strand of the DNA duplex :3'-TACCGATCCGAGCTG-5'
(a)Draw the complementary DNA polynucleotide chain
(b)Construct the RNA molecule, which will'be transcribed.

Very short answer type.
Name two scientists who were awarded Nobel Prize for deciphering DNA structure.

(a) Explain the experiment performed by Griffith on Streptococcus pneumoniae. What did he conclude from this experiment?
(b) Name the three scientists who followed up Griffiths experiments.
(c) What did they conclude and how?

(a) How many codons code for amino acids and how many do not?
(b) Explain the following giving one example of each
(i) Unambiguous and specific codon
(ii) Degenerate codon
(iii) Universal codon
(iv) Initiator codon.

Give one significant contribution of each of the following scientists:
Alec Jeffery

Write the contribution of the following scientists in deciphering the genetic code.
Georce Gamow; Hargobind Khorana; Marshall Nirenberg; Severo Ochoa

Answer the following question in your own word.

Express your opinion about the use of DNA fingerprinting.

Match the names of the scientists with their contributions and choose the correct answer.
Column I - Name of scientists
Column II - Contributions

Identify the correct match between the codons and coding functions.
A) A-2, B-3, C-4, D-1
B) A-1, B-2, C-3, D-4
C) A-4, B-3, C-2, D-1
D) A-3, B-2, C-4, D-1

(a) A DNA segment has a total of 1,500 nucleotides, out of which 410 are guanine containing nucleotides. How many pyrimidine bases this segment possesses?
(b) Draw a diagrammatic sketch of a portion of DNA segment to support your answer.

(a) Write the specific features of the genetic code AUG.
(b) Genetic codes can be universal and degenerative. Write about them, giving one example of each.
(c) Explain aminoacylation of tRNA.