What type of mutation occurs when one nucleotide is replaced by another?

A substitution mutation occurs when one nucleotide in a DNA sequence is replaced by another nucleotide. This type of mutation can lead to different outcomes, including silent mutations, where the amino acid sequence remains unchanged, or missense mutations, which can change one amino acid in the resulting protein, potentially affecting its function. In some cases, substitution mutations can also result in nonsense mutations, where a premature stop codon is created, leading to a shortened and often nonfunctional protein.

This type of mutation is significant because it can affect the genetic code and the protein synthesis process, influencing traits and functions in an organism. Understanding substitution mutations is crucial in discussions of genetic variation, inheritance, and evolutionary biology.