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Addition mutation --> frameshift mutation

(Science: molecular biology) a type of mutation that results from insertion or deletion of a single nucleotide into, or from, an open reading frame in the normal dna sequence.

Normally, the genetic code is read in the wrong frame, three nucleotides at a time, and the entire sequence downstream of the mutation, is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards. These mutations may be induced by certain types of mutagens or may occur spontaneously and usually result in the generation, downstream, of nonsense, chain termination codons.

Synonym: addition mutation, addition-deletion mutation, deletion mutation, reading-frameshift mutation.