Missense mutations or nonsynonymous mutations are types of point mutations where a nucleotide is changed which results in a different amino acid. This in turn can render the resulting protein nonfunctional. Such mutations are responsible for diseases such as Epidermolysis bullosa and sickle-cell disease.
For example, in sickle-cell disease, the 17th nucleotide of the gene for the beta chain of hemoglobin is erroneously changed from the codon GAG (for glutamic acid) to GTG (which codes valine), so the sixth amino acid is incorrectly substituted.
