Missense mutation: A genetic change involving the substitution of one base in the DNA for another which results in the substitution of one amino acid in a polypeptide for another. A missense mutation is a "readable" genetic message although its "sense" (its meaning) is changed. This is in contrast to a nonsense mutation which has no meaning except to halt the reading of the genetic message.

The first missense mutation discovered in humans was found to be responsible for sickle hemoglobin, the molecular basis of sickle cell trait and sickle cell anemia. The mutation causes an amino acid change from glutamic acid to valine, converting normal adult hemoglobin (hemoglobin A) to sickle hemoglobin (hemoglobin S).

The discovery of the sickle missense mutation was made by Vernon Ingram at MIT. In 1956 Dr. Ingram noted that the difference between hemoglobin A and hemoglobin S lay in a single tryptic peptide and then in 1959 reported the precise nature of the missense mutation. This discovery opened the current era of molecular medicine.