Question

The elongation of the leading strand during DNA synthesis

1. progress away from the replication fork.
2. occurs in the $3’\to 5’$direction.
3. produces Okazaki fragments.
4. depends on the action of DNA polymerase.

Short answer

1. The option “progress away from the replication fork” is false.
2. The option “occurs in the $3’\to 5’$direction” is false.
3. The option “produces Okazaki fragments” is false.
4. The option “depends on the action of DNA polymerase” is true.

Step-by-step solution

DNA replication

DNA replication is the process from which new DNA strands are synthesized during the process of cell division. There are more enzymes involved in DNA replication. The existing strand of DNA acts as the template for the new DNA strands.

Explanation of option (A)

The Y-shaped structure formed during the separation of two DNA strands is known as the replication fork. The elongation process proceeds toward the replication fork.

The replication fork direction is the same direction in which the elongation takes place.

Therefore, the given statement is false.

Explanation of option (B)

The elongation is the addition of base pairs in the newly synthesized strand. It always proceeds in the direction of 5’ to 3’.

The 3’to 5’ direction is not the direct propagation of the elongation process.

Therefore, the given statement is false.

Explanation of option (C)

Okazaki fragments are the shorter fragments produced in the lagging strand to accomplish the process of DNA replication. The lagging strand runs in the direction of 3’ to 5’. The replication process does not proceed in this direction.

In order to facilitate the replication in the lagging strand, the Okazaki fragments are synthesized.

The Okazaki fragment is only responsible for the replication of the lagging strand, not the whole DNA.

Therefore, the given statement is false.

Explanation of option (D)

DNA polymerase is the critical enzyme that replicates the DNA strand. It works by adding base pairs to the newly synthesized strand. It is known as the elongation stage.

The elongation phase of DNA replication depends on the activity of the enzymes such as DNA polymerase.

Therefore, the given statement is true.