Question

What does a suppressor mutation suppress? What is the difference between an intragenic and an intergenic suppressor?

Short answer

A suppressor mutation suppresses the phenotypic effects of another mutation, 'suppressing' its effect and often restoring the original phenotype. An intragenic suppressor occurs within the same gene as the original mutation and compensates for the effect of the original mutation, usually by causing an amino acid change that restores the functionality of the protein. An intergenic suppressor, on the other hand, occurs in a different gene from where the original mutation is, and its alteration in the second gene offsets the harmful effects caused by the mutation in the first gene.

Step-by-step solution

Define Suppressor Mutation

A suppressor mutation is a second mutation that alleviates or reverts the phenotypic effects of another mutation. It compensates for the effect of the primary mutation and, in majority of cases, restores the organism's ability to synthesize a specific enzyme or perform a particular function.

Elucidate Intragenic Suppressor

An intragenic suppressor, as the name suggests, occurs within the same gene that carries the original mutation. It may involve a change in a different nucleotide of the same gene that somehow compensates for the effect of the original mutation – most likely by resulting in an amino acid change that restores the ability of the protein to carry out its function.

Clarify Intergenic Suppressor

An intergenic suppressor mutation occurs in a different gene altogether from the one that carries the original mutation. The mutation in the second gene compensates for the detrimental effects of the mutation in the first gene, resulting in a net no change in the phenotype.