Outcomes of point mutations
There are three possible outcomes of a point mutation.
- Silent mutation: the substitution results in a new codon that still codes for the same amino acid. There is no effect on the overall protein structure.
- Missense mutation: the mutation results in the coding of a different amino acid. This results in proteins with different compositions.
Sickle cell anaemia is the result of a missense mutation.
Nonsense mutation: the substitution causes a stop codon to be introduced in a coding sequence. This means that protein translation stops prematurely, resulting in a truncated protein.
The disease thalassaemia is a result of a nonsense mutation of a protein.