3. Are any of the following repair pathways capable of repairing the damage resulting from loss of G by depurination? If so, which one(s)? [Circle all that apply]: (4 points)
a. Direct reversal by photolyase
b. Direct reversal by O6-methylguanine-DNA methyltransferase
c. Mismatch repair
d. Base excision repair
e. Nucleotide excision repair
f. Double-strand break repair by homologous recombination
g. Double-strand break repair by non-homologous end joining?
The answer is (d) base excision repair. An AP site is an intermediate in the base excision repair pathway, so all of the downstream steps of that pathway can be used to repair an AP site. So far as I'm aware, AP sites cannot be repaired by the mismatch repair or nucleotide excision repair pathways (or by any of the other listed pathways).
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