Complementation (genetics)

Article summary

Complementation refers to the capacity of a segment of genetic material (e.g. ) to rescue the phenotype of a mutation. It shows that a copy of the gene affected by the mutation is contained within the segment of genetic material and provides an important criterion for deciding which mutations affect which genes. Complementation can be assessed by mating or crossing strains of an organism that each carry mutations through a simple complementation test. When the mutations in question are homozygous and recessive, complementation will ordinarily result in a normal (or “wild-type”) phenotype if the mutations are in different genes (intergenic complementation). When the mutations are in different genes, each strain's genome supplies the wild-type allele to "complement" the mutated allele of the other strain's genome. Since the mutations are recessive, the offspring that is heterozygous mutant at each gene will display the wild-type phenotype. When the mutations affect the same gene, neither genome can supply a wild type allele and a mutant phenotype results. Such a simple complementation may sometimes produce offspring with a weaker phenotype than one or both parental strains. This still indicates that both mutations likely affect the same gene, since it indicates that the offspring lack completely wild type gene function.…

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