Final answer:
The incorrect insertion of an adenine opposite to guanine in DNA replication leads to a point mutation called a base substitution, which can have significant effects if not corrected by mechanisms like mismatch repair.
Step-by-step explanation:
If during DNA replication, an A (adenine) is incorrectly inserted opposite a G (guanine) in the template DNA strand and the mispairing is not corrected, it will result in a type of mutation known as a point mutation, specifically a base substitution. This type of mutation can have various effects such as silent mutations, which have no effect on protein function, or they can lead to missense mutations (altered amino acid) or nonsense mutations (premature stop codon), which can significantly disrupt protein function. If not corrected by repair mechanisms like mismatch repair, the mutation could be passed to daughter cells, potentially leading to problems such as cancer.