The side-effect of a mutation that affects a primary trait or function on a secondary trait or function.

property of some genes that, when altered, can effect more than one phenotype.

When a single gene has a role in several processes.

The phenomenon of variable phenotypes for a number of distinct and seemingly unrelated phenotypic effects.

The capacity of different alleles of a gene to affect more than one aspect of a phenotype.

Multiple, apparently unrelated phenotypic effects of mutation at a single gene.

The phenomenon whereby a single mutation affects several apparently unrelated aspects of the phenotype.

The ability of a single allele to have more than one distinguishable effect. The most familiar example is the allele responsible for color pattern in Siamese cats.

(plee´ a tro pee) [Gr. pleion: more] • The determination of more than one character by a single gene.

The multiple effects genes can have (intended and unintended).

Situation under which a gene may influences multiple phenotypes (i.e., there is no 1:1 correspondence between gene and behavior)

The effect of a single gene on more than one trait.

Multiple, often seemingly unrelated, physical effects caused by a single altered gene or pair of altered genes

A phenomenon whereby a particular gene affects multiple traits.

One gene that causes many different physical traits such as multiple disease symptoms.

the phenomenon where a single gene is responsible for a number of distinct and seemingly unrelated phenotypic effects

one gene leading to many different phenotypic expressions. An excellent example of a gene with pleiotropic effects is the gene for myotonic dystrophy. Affected individuals can have one or more of a range of signs and symptoms including characteristic Christmas-tree like cataracts, myotonia, narcolepsy, testicular atrophy, frontal balding, mental retardation, and cardiac abnormalities, among others.

Pleiotropy occurs when a single gene influences multiple phenotypic traits. Consequently, a new mutation in the gene will have an effect on all traits simultaneously. This can become a problem when selection on one trait favours one specific mutant, while the selection at the other trait favours another mutant.