Leaky Mutation

A leaky mutation is a type of mutation that partially impairs a certain characteristic or function in the mutant, rather than eliminating it completely. For instance, normal auxotrophic mutants don´t grow at all in the lack of the appropriate medium. However, it is common to find some leaky mutants that grow very slowly in the absence of the appropriate supplements.

In this mutation, the amino acid substitution isn’t enough to completely deactivate a certain function of the protein. Instead, it slows the function or makes it less effective. If the function was completely erased by the amino acid substitution, it would be called a loss-of-function mutation.

Deletions and duplications can be used to distinguish between levels of loss of function so as showed by the picture below.

Figure 1.  Representation of loss of function caused by a leaky mutation (b) and respective phenotype of gene M/+ in this type of situations compared with a control group (a) and respective phenotype of the gene +/+..
Therefore, in leaky mutants is possible observe wild-type phenotype of  this gene due to the allele duplication relative to this gene compensating the loss of function caused by a deletion of an allele of  this gene.