What type of mutation introduces a premature stop codon, truncating the resulting protein?

A nonsense mutation is a type of mutation that results in a premature stop codon in the genetic code of an organism. This occurs because one of the nucleotides in the DNA sequence changes, leading to the substitution of a single amino acid for a stop signal during protein synthesis. As a result, the translation process is terminated early, creating a truncated protein that is often nonfunctional or has reduced functionality compared to the full-length version. This can have significant implications for the organism's phenotype, affecting traits and potentially leading to disease.

In contrast, a missense mutation changes one amino acid in the protein but does not introduce a stop codon, while a silent mutation does not change the amino acid sequence at all, leaving the protein unchanged. A substitution mutation refers to the replacement of one base pair with another, which can lead to various effects, including nonsense mutations, but not all substitutions result in a premature stop codon. Thus, the key characteristic of a nonsense mutation is its ability to produce a stop codon, truncating the protein and affecting its function.