Frameshift mutations

Frameshift mutations are mutation caused by insertions or deletions of a number of nucleotides in a DNA sequence that is not divisible by three. Due to the triplet nature of gene expression by codons, these insertions or deletions change the reading frame, which results in a completely different translation from the original sequence. The earlier in the sequence the deletion or insertion occurs, the more altered the protein.

Figure 1: A deletion of two nucleotides leads to a frameshift and a completely different amino acid sequence.