What is "complementation"

complementation \complementation\ n. (Linguistics) the grammatical relation of a word or phrase to a predicate.

n. 1 (context mathematics English) The replacement of a set by its complement 2 (context genetics English) The interaction between two genetic units such that an organism can function normally if either one is defective 3 (context grammar English) The relationship of a phrase to its predicate

1. n. the grammatical relation of a word or phrase to a predicate

2. (linguistics) a distribution of related speech sounds or forms in such a way that they only appear in different contexts [syn: complementary distribution]

In genetics, complementation occurs when two strains of an organism with different homozygous recessive mutations that produce the same mutant phenotype (for example, a change in wing structure in flies) produce offspring with the wild-type phenotype when mated or crossed. Complementation will occur only if the mutations are in different genes. In this case, 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 will display the wild-type phenotype. A complementation test (sometimes called a " cis-trans" test) can be used to test whether the mutations in two strains are in different genes. Complementation will not occur if the mutations are in the same gene. The convenience and essence of this test is that the mutations that produce a phenotype can be assigned to different genes without the exact knowledge of what the gene product is doing on a molecular level. The complementation test was developed by American geneticist Edward B. Lewis.

If the combination of two genomes containing different recessive mutations yields a mutant phenotype, then there are three possibilities:

1. Mutations occur in the same gene.
2. One mutation affects the expression of the other.
3. One mutation may result in an inhibitory product.