Hi Micaela,

This question is mainly testing your knowledge of base pairing. The PCR aspect of the question helps you understand that the DNA sequence will separate (denaturation), be read, and elongated with the appropriate base pairs.

The question stem tells us that 8-oxo-dG will be preferentially paired to a dA (oxo-dG : dA). So in the first round of PCR we will separate the strands, anneal, and read those base pairs. In this first round oxo-dG will most likely pair again with dA.....and dA will complementary bind to dT.

So even at this point you can see what base has replaced the oxo-dG (you don't need to go the 3 rounds of PCR). We see that dT replaces the oxo-dG and will bind to the dA so that is your answer.

I hope this helps :)

- Shin