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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.