Final answer:
Adenine being paired with cytosine instead of thymine will result in an incorrect base pairing, potentially leading to structural changes in the DNA molecule and other mutations.
Step-by-step explanation:
When a mutation occurs and adenine is paired with cytosine instead of thymine, it will result in an incorrect base pairing. Adenine is supposed to pair with thymine and cytosine with guanine. This incorrect base pairing can lead to structural changes in the DNA molecule and can potentially affect its function. In this case, the DNA strand may bulge or cause other mutations as a response to the incorrect base pairing.