Question

select the correct answer.
in which enzyme would a defect majorly affect the formation of a whole new lagging strand without affecting the leading strand?
a. dna ligase
b. helicase
c. single - strand binding protein
d. topoisomerase

Explanation:

To solve this, we analyze each enzyme's role in DNA replication:

• Option A (DNA ligase): The lagging strand is synthesized as Okazaki fragments. DNA ligase joins these fragments. A defect here would prevent joining lagging - strand fragments, while the leading strand (synthesized continuously) is unaffected.
• Option B (helicase): Unwinds the DNA double helix. A defect would affect both leading and lagging strands since both need unwound DNA to replicate.
• Option C (single - strand binding protein): Stabilizes single - stranded DNA. A defect would impact both strands as they both become single - stranded during replication.
• Option D (topoisomerase): Relieves supercoiling ahead of the replication fork. A defect would affect both strands as supercoiling affects the entire replication process.

Answer:

A. DNA ligase