Question

Which among the following statements is/are correct?

Statement 1: In the double-stranded DNA, only one strand serves as a template for the duplication of the new DNA.

Statement 2: Leading strand is continuously synthesised in 5’-3’ direction and lagging strand is discontinuously synthesised in 3’-5’ direction.

Statement 3: DNA polymerase reads the template strand in 5’-3’ direction.

Statement 4: Replication proceeds only in 5’-3’ direction

Choose the correct option

• A. Statement 1 only
• B. Statement 2 and statement 4
• C. Statement 1 and statement 3
• D. Statement 4 only

Answer 1

The correct option is D Statement 4 only

Replication of DNA is the basis of life. During the S-phase of the cell cycle, the synthesis of DNA takes place in a semi-conservative manner. Each DNA strand serves as the template for the synthesis of a new strand.
Replication proceeds only in the 5’-3’ direction, it is due to the absolute requirement of the free 3’OH group for the polymerisation reaction. The nucleophilic attack on the phosphoryl group of the incoming nucleotide is facilitated by the free 3’OH group, that is why replication proceeds only in 5’-3’ direction in both the leading as well as a lagging strand. DNA polymerase is the main enzyme in the replication of DNA. DNA polymerase reads the template strand in 3’-5’ direction and creates the new strand in 5’-3’ direction.