What does a nonsense mutation cause?

A nonsense mutation introduces a premature stop codon into the coding sequence of a gene, which results in the truncation of the resulting protein. This occurs when a nucleotide change in the DNA sequence leads to the formation of a stop codon (UAA, UAG, or UGA in mRNA), causing the ribosome to halt translation before the protein is fully synthesized. This truncated protein is likely nonfunctional because it does not contain all the necessary amino acids to carry out its intended biological role.

The significance of this mutation is that it can have profound effects on the organism, particularly if the protein is essential for a critical biological function. In contrast, other types of mutations, such as missense mutations, may only change one amino acid without truncating the protein, while silent mutations do not alter the protein at all. Additionally, specific mutations could result in longer proteins, but this is not the case with nonsense mutations, which always lead to shorter polypeptides.