Discussion
Which of the following chemical mutagens are incorporated into the genome by the DNA polymerase during genome replication ?
Answer: B
The mutagens incorporated by DNA polymerase are base analogues.
Base analogues such as 5-bromouracil (a thymine analogue) and 2-aminopurine (an adenine analogue) resemble the normal bases closely enough to be taken up as nucleotides during replication. Once in the DNA they mispair more often than the bases they replace, for example 5-bromouracil pairing with guanine in its rarer tautomer, causing transitions in later rounds.
Alkylating agents such as EMS and deaminating agents such as nitrous acid modify bases already in the DNA. Intercalating agents such as acridines slip between stacked base pairs and cause frameshifts; none of these is built into the chain by the polymerase.
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