Question

Consider a cell in which one of the proteins involved in DNA replication is altered. This alteration results in an increased occurrence of single-stranded DNA breaks in the newly synthesized DNA. Which protein function is most likely nonfunctional in this situation?
A. The unwinding function of helicase
B. The fragment joining function of DNA ligase
C. The winding stress relief function of topoisomerase
D. The proofreading function of DNA polymerase
E. The strand separation function of single-stranded binding protein

Answer 1

Answer:

B. The fragment joining function of DNA ligase

Explanation:

Replication of lagging strand occurs in a discontinuous manner by the formation of short pieces called Okazaki fragments. Okazaki fragments range in length from a few hundred to a few thousand nucleotides. The Okazaki fragments are joined together by DNA ligase enzyme. DNA ligase catalyzes the formation of a phosphodiester bond between a 3' hydroxyl group present at the end of one Okazaki fragment and a 5' phosphate at the end of another fragment.

In the absence of a DNA ligase enzyme, the replicated DNA would have single-stranded breaks as the Okazaki fragments would not have been joined together.