Question

The elongation of leading strand during DNA synthesis
(a) depends on the action of DNA polymerase
(b) produces Okazaki fragments
(c) occurs in 3’ to 5’ direction
(d) progress away from the replication fork

Answer 1

Hint: Replication of DNA occurs from 3’ to 5’ end of parent DNA catalyzed by polymerase enzymes. Okazaki fragments help in the elongation of DNA in the retrograde strand.

Compete step by step answer:
Synthesis of DNA is catalyzed by DNA polymerase III and it is semi discontinuous and bidirectional. The replication of DNA occurs from 5’ to 3’ end on both strands of DNA i.e, leading strand and lagging strand. During the elongation of DNA, incoming DNA is attached to 3’ end of the elongated DNA which is catalyzed by DNA polymerase III.

Additional answer:
- Replication of DNA is semi-conservative where both the strands undergo replication simultaneously producing two daughter molecules
- If the newly synthesized DNA molecules have one half of parental DNA and one half of new DNA it is called the semiconservative method
- initiation of DNA replication occurs at a site called the origin of replication
- DNA consists of two strands leading strand which is continuous moves towards the replication fork and the lagging strand which is discontinuous moves away from the replication fork. Both the strands replicate from 5’ to 3’ end.
The template strand decides the base sequence of a newly synthesized complementary strand
- discontinuously synthesized fragments of DNA on the lagging strand are called Okazaki fragments which are joined together to form a continuous strand of DNA.
- DNA polymerase $\delta$ is responsible for replication and elongation on the leading strand of DNA

So, the correct answer is ‘depends on the action of DNA polymerase’.

Note: There are 5 types of DNA polymerase namely DNA polymerase, DNA polymerase $\beta$, DNA polymerase $\gamma$, DNA polymerase $\delta$, DNA polymerase $\epsilon$.
Along with replication and elongation of DNA, DNA polymerase $\gamma$ helps in proofreading activity
The leading strand of DNA is also called a continuous strand or forward strand and the lagging strand is also called a discontinuous strand or retrograde strand.