What occurs during a base substitution mutation?

During a base substitution mutation, one type of nucleotide base in the DNA sequence is replaced by a different type of base. This alteration can lead to a change in the corresponding amino acid in a protein, potentially altering its structure and function. Base substitution mutations can occur in several forms, including silent mutations, which do not change the amino acid sequence, missense mutations, which lead to a different amino acid being incorporated, and nonsense mutations, which create a premature stop codon. This type of mutation is significant because it can influence gene expression and the resulting phenotype of an organism, depending on the specific base that is replaced and where in the DNA sequence it occurs.

In contrast, replacing all bases with new bases or adding or deleting bases represents different types of mutations, such as frameshift mutations, rather than a simple substitution. Therefore, the correct understanding of a base substitution mutation is focused solely on the replacement of one base for another, which can have varying effects on the resulting protein.