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CBSE Questions for Class 12 Medical Biology Molecular Basis Of Inheritance Quiz 8 - MCQExams.com
CBSE
Class 12 Medical Biology
Molecular Basis Of Inheritance
Quiz 8
Scientists who shared Nobel Prize with Khorana for interpretation of genetic code were
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Nirenberg and Holley
0%
Watson and Crick
0%
Cohen and Boyer
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Wilmut and Campbell
Explanation
Har Gobind Khorana shared the 1968 Nobel Prize for Physiology or Medicine with Marshall W. Nirenberg and Robert W. Holley for research that showed the order of nucleotides in nucleic acids, which carry the genetic code of the cell and control the cell’s synthesis of proteins.
So, the correct option is 'Nirenberg and Holley'.
Which of the following enzymes is not required for DNA synthesis?
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Ligase
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DNase
0%
DNA polymerase
0%
RNA polymerase
Explanation
DNA synthesis is done with the help of Helicase, DNA polymerase, Ligase, and Primase enzymes. Ligase joins DNA strands called Okazaki fragments
by catalyzing the formation of phosphodiester bond.
Deoxyribonuclease or DNase is an enzyme that breaks the DNA into nucleotides, i.e. degrades the DNA. DNA polmerase is used to make DNA from nucleotides. RNA polmerase helps in replication. Hence, the correct answer is B.
Human genome contains base pairs
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2.5 million
0%
25 million
0%
27.2 million
0%
3.2 billion
Explanation
There are four bases adenine (A), thymine (T), guanine (G) and cytosine (C) present in humans. Bases on opposite strands pair specifically as an A always pairs with a T, and a C always with a G. The human genome contains approximately 3.2 billion of these base pairs, which reside in the 23 pairs of chromosomes within the nucleus of all our cells.
So, the correct option is '3.2 billion'.
Human genome project was launched in
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1980
0%
1987
0%
1990
0%
1993
Explanation
Human Genome Project was launched in 1990 by coordination of US Department of Energy and National Institute of Health. The 13-year mega project was aimed to sequence complete 3 billion DNA base pairs that make up human genome. So, the correct answer is ' 1990'.
Human genome project was launched by
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Khorana and others
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Bhabha Institute
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U.S Department of Energy and National Institute of Health
0%
NASA
Amino acid binding site of tRNA has
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CCA - OH
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CGA - OH
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UCA - OH
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UCG - OH
Explanation
Transfer ribonucleic acid or tRNA is a type of RNA molecule that serves as an adaptor in translating the language of nucleic acids into the language of proteins. They are relatively small and consist of a single strand of RNA folded into a precise three-dimensional structure (the cloverleaf secondary structure). Most tRNAs have
a guanylate (
pG
) residue at the 5' end and all have the
trinucleotide sequence CCA (3') at the 3' end.
The CCA tail of the amino acid arm is a cytosine-cytosine-adenine
sequence at the 3' end of the tRNA molecule. The amino acid loaded onto the tRNA by aminoacyl tRNA synthetases, to form aminoacyl-tRNA,
is covalently bonded to the 3'-hydroxyl group
on the CCA tail. This sequence is important for the recognition
of tRNA by enzymes and critical in translation. Therefore, option A is correct answer.
DNA is unique in that it has
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Nitrogen bases
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Ability to withstand heat
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Ability to replicate
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Ability for replication and transcription
Explanation
DNA is genetic material found in the living cell. It helps to carry characters from one generation to the other. The process by which the DNA replicated and forms another DNA molecule is known as replication. Parent strand of the DNA strand act as a template for synthesis of another DNA molecule.
Transcription is the process by which DNA is converted into RNA. The enzyme RNA polymerase plays an important role in transcription. The sequence of the nitrogenous base on the DNA acts as a template and determines the sequence of the nitrogenous base on the m-RNA.
So, the correct answer is option D.
Number of genes present in human genome is about
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15,000
0%
21,000
0%
27,000
0%
30,000
Explanation
A gene is a distinct sequence of nucleotides forming part of a chromosome.
Most of the genes do not code for proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project estimated that humans have around 21,000 genes.
So, the correct option is '21,000'.
Double helical structure of DNA was proposed by
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Kornberg
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Nirenberg
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Watson and Crick
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Wilkins and Franklin
Explanation
Double helical structure of DNA was proposed by Watson and Crick.
DNA is made up of a nitrogenous base, phosphate, and sugar.
DNA and RNA are the chain of polynucleotide which are joined by the phosphodiester bonds. The two nucleotide is linked by the phosphodiester bond. It is formed by the linkage between the 3' carbon atom of one sugar molecule and the 5' carbon atom of another.
The two strands are antiparallel as one runs in 5'-3' direction as the 3' end of sugar is attached to the phosphorous and the other strand is complimentary which runs in 3'-5' direction where 5' end of sugar is attached to the phosphorous.
So, the correct answer is option C.
Watson and Crick were awarded Nobel Prize for their finding of
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RNA is single stranded
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DNA is double stranded
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DNA is genetic material
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DNA guides mRNA synthesis
Explanation
Nucleic acids were first discovered by Fredrick Meischer in the nuclei of pus cells. Double helical structure of DNA was proposed by Watson and Crick. DNA and RNA are the chain of polynucleotide which are joined by the phosphodiester bonds. The two nucleotide is linked by the phosphodiester bond. It is formed by the linkage between the 3' carbon atom of one sugar molecule and the 5' carbon atom of another. The two strands are antiparallel as one runs in 5'-3' direction as the 3' end of sugar is attached to the phosphorous and the other strand is complimentary which runs in 3'-5' direction where 5' end of sugar is attached to the phosphorous.
So, the correct answer is option B.
Which option shows correctly labelled region in the given diagram of DNA replication?
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A, C
0%
Only C
0%
A,B
0%
B, C
Griffith effect is
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DNA transcription
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RNA translation
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Bacterial transformation
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Bacterial transduction
The area of unwinding and separation of DNA strands during replication is called
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Origin
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Initiation point
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Primer
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Replication fork
Double helix model of DNA was proposed by
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Nirenberg
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Komberg
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Holley and Nirenberg
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Watson and Crick
Explanation
Watson and Crick suggested the double helix model of DNA. He stated 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 ad 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.
Thus, the correct answer is option D.
The most exciting discovery of life science, which can possess only four biochemical letter
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Genetic code
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Transcription
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Translation
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Flybridsation
Explanation
The process by which the information coded in RNA (mRNA) is decoded into a polypeptide is called as the genetic code. This decoding polypeptide Is one of the most exciting discoveries in life science. The most important feature of the genetic code is that it is a triplet codon and possess only four biochemical letters, namely, A-Adenine, G-Guanine, C-Cytosine, U-Uracil.
Thus, the correct answer is option A.
One turn of DNA possesses
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One base pair
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Two base pairs
0%
Five base pairs
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Ten base pairs
The enzyme, which helps to cut one strand of DNA duplex to release tension of coiling of two strands is
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DNA ligase
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DNA polymerase
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Topoisomerase
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Swielases
Explanation
Helicase is the enzyme which unwinds the helix (by disturbing H-bonds), while topoisomerases have the ability to break and releases the tension of strands of DNA.
DNA ligase is the enzyme which helps in joining the Okazaki segments which form the lagging strand.
DNA polymerase-I removes the RNA primer and helps in the formation of oligodeoxyribonucleotide chain in its place for completing the replication.
So, the correct answer is option C.
New strand formation on a DNA template can be initiated only by ________________.
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DNA polymerase I
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DNA polymerase III
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RNA primer
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DNA primer
In Streptococcus pneumoniae
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Virulent form is smooth
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Virulent form is rough
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Nonvirulent form is capsulated
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All forms are rough
Bacterium in which transformation was first studied is
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Salmonella typhimurium
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Streptococcus pneumoniae
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Escherichia coli
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Streptococcus aureus
DNA replication is
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Conservative and discontinuous
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Semiconservative and semidiscontinuous
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Semiconservative and discontinuous
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Conservative
GUG specifies amino acid valine. However, when functioning as initiation codon it specifies _____________.
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Methionine
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Valine
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Lysine
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Isoleucine
Explanation
Start codon indicates where to start the translation. The start codon specifies the amino acid methionine and is denoted by code AUG.
However, if AUG is absent, then GUG acts as a start codon and codes for methionine. So, most polypeptides begin with this amino acid.
So, option A is correct.
In the genetic dictionary, there are 64 codons as
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64 amino acids are to be coded
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64 types of tRNAs are present
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There are 44 nonsense codons and 20 sense codons
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Genetic code is triplet
Explanation
There are 20 amino acids and each codon is triplet; it consists of 3 nitrogeneous bases constituting a particular amino acid.
There are 4 nitrogeneous bases ie. AUGC in case of RNA. So, since each codon consists of 3 bases so total possibilities of combination would be 4^3 = 64.
Now out of these 64 codons 61 codons code 20 amino acids. It is to be remembered that one amino acid can be coded by one or more codons.
The rest 3 ie. UGA, UAA and UAG are termination codons ie. they don't code for any of the 20 amino acids.
So, the correct option is 'Genetic code is triplet'.
Experimental material in the study of DNA replication has been
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Escherichia coli
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Neurospora crassa
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Pneumococcus
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Drosophila melanogaster
Functional unit of gene that specifies synthesis of one polypeptide is
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Codon
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Cistron
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Recon
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Muton
Usual method of DNA replication is
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Semiconservative
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Conservative
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Dispersive
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Nonconservative
In operon model, RNA polymerase binds to
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Structural gene
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Promoter gene
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Regulator
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Operator gene
The transforming principle of Pneumococcus as found out by Avery, MacLeod and McCarty was
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mRNA
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DNA
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Protein
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Polysaccharide
What is true of Watson and Cricks model of DNA. It is duplex with ______.
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10 base pairs and 34$$A^\circ$$ distance for every turn
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10 base pairs and 3.4
$$A^\circ$$
distance for each turn of spiral
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20 base pairs and 34
$$A^\circ$$
for each turn
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10 base pairs and 34 nm distance for every turn
Characters are transferred from parents to progeny through
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DNA
0%
RNA
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Protein
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Phospholipid
Arrangement of three successive bases in genetic code signifies
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Protein
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Amino acid
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Nucleic acid
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Plasmid
Double Hydrogen bonds occur in DNA between ___ and ___.
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Adenine and Thymine
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Uracil and Thymine
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Adenine and Guanine
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Thymine and Cytosine
tRNA recognises ribosome by ____________.
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TC loop
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DHU loop
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Anticodon
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AA-site
Enzyme required for removing RNA primer during DNA replication is ______________.
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Primase
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DNA polymerase I
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DNA polymerase III
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Ligase
The number of base substitution possible in amino acid codons is
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261
0%
264
0%
535
0%
549
Explanation
There are 61 codons for amino acids. Each codon has 3 bases, each of which can undergo transition and transversion substitution, 61 x 3$$^2$$ = 549.
So, the correct answer is '549'.
Cytosine base inserted in the beginning of DNA codons ATGATGATG will produce
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CATGAGGATT
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CATGATGATG
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CATGATGATG
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Nonsense mutation
Genetic code was discovered by frameshift mutation by
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Crick
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Watson
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Franklin
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Khorana
Transformation experiments in bacteria were first performed by
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Macleod
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Griffith
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Pasteur
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Meselson and Stahl
Isotopes used in proving semi-conservative replication of DNA were
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$$^{14}N, ^{14}C$$
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$$^{14}C, ^{31}P$$
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$$^{14}N, ^{15}N$$
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$$^{14}N, ^{31}P$$
Type of coiling in DNA is
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Right handed
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Left handed
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Zigzag
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Opposite
DNA is present in
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Nucleus
0%
Chloroplasts
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Mitochondria
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All the above
Explanation
Correct answer:
D
Explanation:
•
DNA is mainly found in the
nucleus,
however, extranuclear DNA is found in certain organelles.
•
Mitochondrial DNA
is significant in maternal inheritance, whereas
chloroplast DNA
consists of genes important for photosynthesis.
Hence, DNA is present in
all of the above.
Genetic code translates the language of __________________.
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Amino acids into that of RNA
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RNA into that of protein
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Protein into that of DNA
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RNA into that of DNA
In a DNA molecule cytosine is 18%. Percentage of adenine would be _________.
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0%
32%
0%
64%
0%
36%
0%
18%
Explanation
The answer is option A i.e "32%".
According to Chargraff's rule, Number of purine (adenine+guanine) = Number of pyrimidine (cytosine+thymine).
Hence, the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.
As per the data given above, we can infer that, the percentage of G = the percentage of C = 18%.
Now, total percentage of total A and T = 100 - 18 - 18 = 64, so the percentage of A is 64/2 = 32%.
tRNA has two unequal free arms _________________.
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Short arm ending in - G and long arm in - CCA
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Short arm ending in - A and long arm in - ACC
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Short arm ending in G and long arm in - CGA
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Short arm ending in C and long arm in GCA
Correct sequence of code transfer during polypeptide formation is
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DNA, mRNA, tRNA and amino acids
0%
DNA, tRNA, rRNA and mRNA
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mRNA, tRNA, DNA and amino acids
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rRNA, DNA, mRNA and tRNA
Which one is involved in DNA repair ?
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Ligase
0%
Primase
0%
DNA polymerase III
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DNA polymerase I
tRNA has the function of ___________________.
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Transcription
0%
Adapter for attaching amino acids over mRNA template
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Transferring information to mRNA
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Carry genetic code to cytoplasm
A single amino acid is often coded by more than one triplet codon. In most of these cases the first two bases are the same but the third base is different. The feature of genetic code is
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Universality
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Nonoverlapping and commaless
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Redundancy and degeneracy
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Nonambiguity
DNA was proved to be genetic material through experiment of
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Transduction
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Replica experiment
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Viral infection of Tobacco
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Transformation
Out of 64 codons, 61 code for 20 types of amino acids. It is due to
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Overlapping genes
0%
Degeneracy of genetic code
0%
Wobbling of codons
0%
Universality of codons
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