A type of gene mutation wherein the addition or deletion of (a number of) nucleotide(s) causes a shift in the reading frame of the codons in the mRNA, thus, may eventually lead to the alteration in the amino acid sequence at protein translation.
Reading-frameshift mutations may be beneficial, deleterious, or lethal. For example, induction of frameshift mutation has been used to make certain bacteria capable of producing nylonase, an enzyme that can degrade nylon. They have also been one of the possible causes of albinism. A shift in the reading frame can lead to formation of stop codon, hence, early terminating protein translation. An early termination of any of the enzymes necessary for the production of melanin can result in albinism.