What is the function of topoisomerase? a. relieving strain in the DNA ahead of the replication fork b. elongation of new DNA at a replication fork by addition of nucleotides to the existing chain c. the addition of methyl groups to bases of DNA d. stabilizing single-stranded DNA at the replication fork e. unwinding of the double helix

A - Relieving strain in the DNA ahead of replication fork.

Explanation:

During transcription or replication, DNA double helixed strand unwinds catalysed by the helicase enzyme, they break the hydrogen bonds that holds the two strands together. When DNA unwinds, supercoils are created in the replication fork, if it is not dealt with, transcription or replication will come to a halt. Topoisomerase enzymes are there to relieve DNA by cutting the phosphate backbone of either single or both strands of DNA, preventing supercoils.