The 3'-5' exonuclease activity of DNA polymerase is critical for:

a. The removal of the thymine dimers induced by UV light.

b. The fidelity of DNA synthesis.

c. Separating two DNA molecules after replication.

d. The removal of the RNA primers from the lagging strand.

e. The conversion of the HIV-RNA to DNA

Answer: b). The fidelity of DNA synthesis.

Explanation: The 3'->5' exonuclease activity of DNA polymerase is to double - check every nucleotide after it is added to the growing strand in order to remove mismatched base pairs. When a wrong nucleotide is added by the DNA polymerase, translocation of the enzyme to where the next nucleotide will be added will be inhabited, therefore the 3'->5' exonuclease activity removes the mispaired nucleotide so that replication can continue. This activity is called proofreading. This activity ensures the accuracy of DNA synthesis.

Answer: Option B) The fidelity of DNA synthesis.

Explanation:

In DNA synthesis, some enzymes known as DNA polymerases, catalyze the addition of nucleotides to elongate the already formed DNA chain.

Then, 3'-5' exonuclease activity of DNA polymerase is introduced for proofreading i. e to remove wrongly paired nucleotides from the 3' end of the DNA chain.

Thus, 3'-5' exonuclease activity of DNA polymerase is critical for fidelity of DNA synthesis.