Question

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA during DNA replication? A The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction. B The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end. C The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together. D The leading strand is synthesized at twice the rate of the lagging strand.

Answer 1

The answer is; A & C

The lagging strand is replicated in fragments called Okazaki fragments, each initiated by a primer. The fragments are later joined into one strand by DNA ligase. Replication occurs by adding nucleotides to the 3’ end of a preceding nucleotide. Because the lagging strand is antiparallel to the leading strand, the replication of the lagging strand is in the opposite direction as the replication fork direction. This is why the lagging strand is replicated in fragments because replication is being carried out by a single DNA polymerase (moving in the direction of the replication fork) per replication fork.