views updated

frameshift An alteration in the sequence of DNA bases read as base triplets during transcription, caused by the deletion (or addition) of a single nucleotide in the DNA sequence. The missing (or additional) base results in an abnormal triplet and also causes each subsequent triplet group to be altered. A frameshift mutation therefore produces messenger RNA with corresponding changed codons and results in the synthesis of an abnormal protein. For example, the deletion of uracil (U) in the second codon of the following mRNA sequence: AUU  CAU  CGG  UAG  ACC  UGU  AUG

results in the frameshifted sequence: AUU  CAC  GGU  AGA  CCU  GUA  UG