Question

the model represents dna replication.
which statement best describes structure 2?
a. it is the lagging strand because it uses rna primers.
b. it is the lagging strand because it is being built in short segments.
c. it is the leading strand because the 5 end is closer to the replication fork.
d. it is the leading strand because it is being built in the 3 to 5 direction.

Explanation:

In DNA replication, the leading strand is synthesized continuously in the 5' to 3' direction. The lagging strand is synthesized discontinuously in short segments (Okazaki fragments) because DNA polymerase can only add nucleotides in the 5' to 3' direction. RNA primers are used to initiate synthesis of both strands, but the key characteristic of the lagging strand is its discontinuous synthesis in short segments. Option A correctly identifies Structure 2 as the lagging strand based on this key feature. Option B's reasoning about the 5' end proximity is not the defining characteristic. Options C and D incorrectly label it as the leading strand.

Answer:

A. It is the lagging strand because it uses RNA primers.