CBSE Questions for Class 12 Medical Biology Molecular Basis Of Inheritance Quiz 7 - MCQExams.com

• DNA fingerprinting is a technique that is used by the scientist to distinguish between individuals of the same species using their DNA by the order of the base pairs.
• This technique was invented by the genetic scientist Alec Jeffrey who was a professor and geneticist at the University of Leicester in the UK.

$$\textbf{Correct option: B}$$

$$\textbf{Solution:}$$

Option B:

$$\bullet$$ Human genome project (HGP) was an international project based on sequencing the entire genome of human (3.3 billion base pairs). This project was successfully completed in 2003.

$$\bullet$$ The HGP accelerated the growth of bioinformatics, a vast field of study. The successful sequencing of the human genome could solve the mystery of many human disorders. It does not eliminate all the diseases, but provide us with a way to cope with them.

$$\bullet$$ The main aims of Human Genome Project are:

1. Data analysis optimization.
   
2. The whole genome is being sequenced.
   
3. Identification of the entire human genome.
   
4. Building genome sequence databases to store the data.
5. Taking care of any legal, ethical, or social issues that might be raised during project.

Hence the correct option is option B.

• The Human Genome Project was an international effort to determine the DNA sequence of the entire Human Genome and the mapping of genes that are present in humans.
• It is found that there are around 30000 to 40000 genes present in humans and 97% of the inactive DNA material contains around 50 percent of repetitive DNA material which makes around two-third of the sequence consisting of repetitive elements in humans.

• The first codon on mRNA is known as the initiation codon. 
• AUG is the start codon of mRNA which codes for amino acid methionine in eukaryotes and modified fMet in prokaryotes.
• fMet is formylmethionine which is peculiar amino acid coded in prokaryotes. It is the first codon at which the translation of proteins begins, it is paired during the translation with the tRNA with anticodon UAC.

• Topoisomerases are ubiquitously expressed enzymes that overcome topological problems in genomic DNA, which can result from DNA replication, transcription and repair.
• Positive supercoiling and tangles are resolved by topoisomerases by catalyzing the breaking of one or two strands of DNA. 
• This will release the supercoiling and torsional tension of DNA by transiently cleaving and rejoining one strand of the DNA duplex. 
• Helicases move along the double-stranded DNA and separate the strands by breaking hydrogen bonds.
• DNA Ligase enzyme joins two large molecules by forming a new chemical bond like phosphodiester bond. 

• AUG or methionine codon is a sense codon having a dual function. Duality in the codon function is known in the initiation of translation and methionine insertion into internal protein positions.
• When AUG is at the beginning of prokaryotic message (initiation codon), it codes for the incorporation of N- formyl methionine (fMet) whereas AUG within the message code for normal methionine (Met). UGA (opal), UAG(amber) and UAA (ochre) are non-sense codons as they do not specify any amino acid and when present in the reading frame lead to polypeptide chain termination.

• 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 strands of the DNA molecule together to form the helix. 
• Thus, the correct answer is option A. 

• The model of DNA was given by Watson and Crick in the year 1953. It is the hereditary molecules that are responsible for carrying the characters from parents to offspring.
• The DNA is in the $$B$$-form that shows left-handed coiling.
• The  spiral length is $$34 \mathring { A } $$ and its diameter of $$20 \mathring { A } $$. One spiral turn has $$10$$ base pairs. 
  Thus the correct answer is option A.

• The model of DNA was given by Watson and Crick in the year 1953. It is the hereditary molecules that are responsible for carrying the characters from parents to offspring. 
• The DNA is in the $$B$$-form that shows right-handed coiling. The spiral length is $$34 \mathring { A } $$ and its diameter of $$20 \mathring { A } $$. One spiral turn has 10 base pairs. 
• Thus, the correct answer is option A.

• As DNA polymerase replicates DNA only in 5' to 3' direction, replication in the strand with 3'-5' polarity is continuous. 
• While replication in 5'-3' strand, is discontinues. The lagging strand is synthesized in short, separated segments. On the lagging strand template, a primase "reads" the template DNA and initiates synthesis of a short complementary RNA primer. A DNA polymerase extends the primed segments, forming Okazaki fragments. The RNA primers are then removed and replaced with DNA, and the fragments of DNA are joined together by DNA ligase.
• So, the correct option is 'Discontinuously'.

• The DNA in humans is a double helix. Pitch is the number of base pairs in one complete turn of the helix. 
• There are 10 base pairs in 1 complete turn and the distance between 2 bases is 0.34nm. 
• The deflection between two successive base pairs has a pitch angle of 36$$^o$$. 
  Thus the correct answer is option C.

DNA fingerprinting refers to the molecular analysis of the profile of DNA samples, short nucleotide repeats are important for DNA finger printing which vary in number from person to person but are inherited. These are variable number tandem repeats (VNTRs) and can be recognized only through molecular analysis of DNA simples. Allec Jafferys (1985) discovered this technique for the first time in England.

• 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 and how these nucleotides carry the genetic code of the cell and control the cell’s synthesis of proteins. 
  
• So, the correct option is '1968'.

Correct option: B

Explanation:

· DNA replication is a process in which DNA makes a copy of itself. Crick proposed three types of DNA replication conservative method, dispersive method, and semi-conservative method from an experiment which was concluded that DNA is replicated in the semi-conservative method.

· Types of DNA replication depend on the cell. In a prokaryotic cell, the DNA is circular and it is replicated in theta model, and in a eukaryotic cell, DNA is linear it is replicated in a Y-shaped replicating fork. 

· Steps of DNA replication:

1. Activation of all the nucleotides dNTP's inactive nucleotides are activated with the help of ATP and the enzyme phosphorylase.

2. Origin of replication with respect to cells prokaryotic cells have small DNA so only one origin of replication is there eukaryotic cells as it has larger DNA meaning origin of replication are there.

3. Nick, cut, and incision in DNA it is done at the origin of replication after the cut of hydrogen bonds break by the help of enzyme endonuclease.

4. Unwinding unzipping of DNA is done with the help of the enzyme DNA helicase or rep protein. It is done by breaking all the hydrogen bonds.

5. Use of single-stranded binding protein (SSBP) to prevent enter coiling of unwinded DNA. 

6. Release of tension caused due to winding of DNA due to unwinding the upper DNA can undergo tension and stress to release it topoisomerase enzyme is used which is also known as DNA gyrase.

7. Formation of RNA primer is a small fragment, RNA synthesized with the help of enzyme DNA primase. RNA primer always binds to the 3 prime end of DNA.

8. Synthesis of DNA in disturbs new DNA strand is synthesized by the help of DNA polymerase enzyme. DNA polymerase can add nucleotides on 5 prime to 3 prime direction of strand. DNA polymerase attracts all the activated dNTP's with respect to the template and new DNA is synthesized. 

Hence, ‘Replication’ is the correct answer.