Questions: Every 24 hours, our cells have mutations occurring in the DNA. Given the possible DNA repair mechanisms, which enzyme will first help proofread and fix the errors? Multiple Choice DNA polymerase Glycosylase SOS repair enzymes Exonuclease Prev 19 of 27 Next

The answer is the first one: DNA polymerase.

Explanation for each option:

1. DNA polymerase: This enzyme is primarily responsible for DNA replication and has proofreading abilities. During DNA replication, DNA polymerase can identify and correct errors by removing the incorrect nucleotide and replacing it with the correct one. This proofreading function is crucial for maintaining DNA integrity and is the first line of defense against mutations during replication.

2. Glycosylase: This enzyme is involved in base excision repair, a process that removes damaged bases from DNA. While important for repairing specific types of damage, glycosylase does not play a role in the initial proofreading during DNA replication.

3. SOS repair enzymes: These are part of a bacterial response to extensive DNA damage. The SOS response involves a set of enzymes that can bypass lesions in the DNA, but they are not involved in the initial proofreading process during normal DNA replication.

4. Exonuclease: This enzyme can remove nucleotides from the ends of DNA strands. While some DNA polymerases have exonuclease activity for proofreading, the term "exonuclease" alone does not specify the proofreading function during DNA replication.

In summary, DNA polymerase is the enzyme that first helps proofread and fix errors during DNA replication.