Final answer:
Substitution of guanine for thymine would be a transversion substitution mutation that may distort the DNA structure. Deamination of cytosine to uracil can lead to a permanent G-C to A-T transition if not repaired, affecting protein synthesis. Repair mechanisms can correct these errors by excising incorrect bases and replacing them with correct ones.
Step-by-step explanation:
DNA Mutation and Repair Mechanisms
During the production of a gamete, if guanine were to replace thymine in a growing strand of DNA, this would constitute a type of mutation known as a transversion substitution. This occurs when a purine (like guanine) is replaced by a pyrimidine (like thymine), or vice versa, which can significantly affect the DNA structure as a purine is larger than a pyrimidine. Normally, adenine pairs with thymine, and guanine pairs with cytosine. If there is erroneous base pairing, such as guanine pairing with thymine, the DNA's double helix may be distorted.
Deamination is a process that frequently involves cytosine being converted into uracil, ultimately leading, after DNA replication, to a G-C to A-T base pair substitution if not repaired. The DNA replication machinery recognizes adenine and thymine as a correct pairing, thus perpetuating the mutation. In cases where adenine replaces cytosine, the impact on DNA structure can range from no change to potential errors in protein synthesis if mismatch repair mechanisms do not correct the mistake.
Correction mechanisms involve excising the incorrect bases and replacing them with the correct ones. When DNA polymerase encounters a mismatch due to mutation, it can identify the non-methylated, newly synthesized strand and remove the wrongly incorporated bases. If left uncorrected, such mutations can have varying phenotypic effects, depending on their location and consequence within the genome.