What type of mutation involves a change in a single nucleotide base in the DNA?

A mutation that involves a change in a single nucleotide base in the DNA is known as a point mutation. This type of mutation can occur in several ways, typically through the substitution of one base for another. In essence, point mutations lead to a change in a specific codon, which can ultimately affect the amino acid sequence during protein synthesis.

Point mutations can take two forms: silent mutations, where the change does not affect the amino acid produced, and missense or nonsense mutations, which can result in a different amino acid or a premature stop codon, respectively. The defining characteristic is that it affects only one base pair, which sets it apart from other types of mutations like frameshift mutations, where one or more bases are inserted or deleted, resulting in a shift in the reading frame of the genetic code. This distinction illustrates why point mutations are specifically categorized as such and highlights the importance of single nucleotide changes in genetic variation and the potential consequences for organism function.