Question

Below are four types of mutation that can occur in an exon sequence. Which is likely to cause the largest change to the resulting protein?

(A) Single base pair deletion

(B) Three base pair deletion

(C) Missense mutation

(D) Synonymous mutation

Answer 1

The largest change to the resulting protein can be caused by:

(A) Single base pair deletion

This will cause the deletion of a single nucleotide base resulting in a shift in the reading frame of amino acids. The reading frame is in multiples of 3 with an amino acid made for every 3 nucleotide combinations. But the deletion of one base pair will shift the entire frame and produce a totally different protein. It may even introduce or abolish a stop codon resulting in a non-functional protein thus making them the most dangerous mutations.

Three base pair deletion only delete one amino acid from the chain. Since it does not shift the entire reading frame, the effects are not as dangerous.

Missense mutation is the change of an amino acid to another amino acid. Not all missense mutations are dangerous, some are conservative or silent in nature.

Synonymous mutations only change one codon or nucleotide base without changing the amino acid it translates into. As the genetic code is degenerate, it makes the mutation neutral in nature.