frameshit mutation occurs when

1. bese is deleted
2. base is deleted or added
3. base is added
4. anticodons are not present

Aframeshift mutationis agenetic mutationcaused by indels(insertionsordeletions) of a number ofnucleotidesin a DNA sequence that is not divisible by three. Due to the triplet nature ofgene expressionbycodons, the insertion or deletion can change thereading frame(the grouping of the codons), resulting in a completely differenttranslationfrom the original. The earlier in the sequence the deletion or insertion occurs, the more altered the protein.