Question

In nucleic acid synthesis, why does the leading strand proceed in the 5'-3' direction, while the lagging strand proceeds in the 3'-5' direction, resulting in Okazaki fragment formation?

A) Replication machinery moves in one direction only.
B) The template strand dictates the direction of synthesis.
C) Okazaki fragments are formed due to errors in replication.
D) DNA polymerase can only add nucleotides in the 5'-3' direction.
Please select the correct option.

Answer 1

The synthesis of the leading strand proceeds continuously in the 5'-3' direction, while the lagging strand is synthesized in Okazaki fragments due to the orientation of the template strands and the directionality of DNA polymerase activity.

Step-by-step explanation:

In nucleic acid synthesis, DNA polymerase can only add nucleotides in the 5'-3' direction.

Thus, the leading strand is synthesized continuously in the 5'-3' direction towards the replication fork.

In contrast, since the other template strand runs antiparallel, the lagging strand must be replicated in segments, called Okazaki fragments, in the 5'-3' direction away from the replication fork, making use of multiple RNA primers.

Later, these fragments are joined together by DNA ligase to form a continuous strand.

The correct answer to why the leading strand proceeds in the 5'-3' direction while the lagging strand proceeds in the 3'-5' direction, resulting in Okazaki fragment formation, is D) DNA polymerase can only add nucleotides in the 5'-3' direction.