What Is a Frameshift Mutation?

Frame shift mutation refers to a change in reading frame caused by the deletion or insertion of a base in a DNA molecule, resulting in a series of changes in the downstream code. Completely different peptide sequence. For example, the mRNA of a gene is: GAA GAA GAA GAA ..., and the translation product is a glutamic acid polypeptide. If you insert a G at the beginning Then the mRNA reading frame becomes GGA AGA AGA AGA ..., and the translation product is an arginine polypeptide starting with glycine. Frameshift mutations will inevitably cause changes in the properties of proteins and thus variability in traits. In severe cases, individuals will die. ^[1] DNA damage caused by frameshift mutations is generally much greater than point mutations. ^[2]

A frame shift mutation is a DNA sequence

Conversion and transversion only involve a pair of bases, which are typical point mutations. The result is

The mechanism for suppressing frameshift mutations is not very clear, but in Salmonella, several genes that can inhibit frameshift mutations have been found, and it has no inhibitory effect on nonsense and missense mutations. Think of it this way: ^[5]

Take eukaryotes as an example.

Codon table

For example, the base sequence of the DNA template chain is: TAC CAT TAG GAT CCC ATT, and the transcribed mRNA base sequence is: AUG GUA AUC CUA GGG UAA The amino acid sequence determined by the genetic code is: methionine (starting code ) Valine isoleucine Leucine Glycine termination code ^[4]

If a C is inserted between the 3rd and 4th bases after the transcription start site of the DNA template strand, the base sequence of the DNA template strand becomes: TAC CCA TTA GGA TCC CAT T transcribed mRNA base The sequence becomes: AUG GGU AAU CCU AGG GUA A. The amino acid sequence determined by the genetic code becomes: methionine (start code) glycine aspartic acid proline arginine valine, translated polypeptide chain The amino acid sequence has changed dramatically. ^[4]

If the 7th base T after the transcription start site of the DNA template strand is lost, the base sequence of the DNA template strand becomes: TAC CAT AGG ATC CCA TT The mRNA base sequence transcribed becomes: AUG GUA UCC UAG GGU The amino acid sequence determined by the AA genetic code becomes: methionine (start code) valine serine stop code. The amino acid sequence of the translated polypeptide chain has also changed greatly compared to the original.