In genetics, a missense mutation (a type of nonsynonymous substitution) is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. Another type of nonsynonymous substitution is a nonsense mutation in which a codon is changed to a premature stop codon that results in truncation of the resulting protein. Missense mutations can render the resulting protein nonfunctional, and such mutations are responsible for diseases such as Epidermolysis bullosa, sickle-cell disease, and SOD1 mediated ALS.