will in general cause the reading of the codons after the mutation to code for different amino acids. The frameshift mutation will also alter the first stop codon ("UAA", "UGA" or "UAG") encountered in the sequence. The polypeptide being created could be abnormally short or abnormally long, and will most likely not be functional.

Frameshift mutations are apparent in severe genetic diseases such as Tay-Sachs disease; they increase susceptibility to certain cancers and classes of familial hypercholesterolaemia;