Gene complex

A supergene is a group of neighbouring genes on a chromosome which are inherited together because of close genetic linkage and are functionally related in an evolutionary sense, although they are rarely co-regulated genetically.

Supergenes have cis-effects due to multiple loci (which may be within a gene, or within a single gene's regulatory region), and tight linkage. They are classically polymorphic, and different elements code for different fitness effects which combine to form a coherent or epistatic whole. The two classic supergenes are (1) the Primula heterostyly locus, which controls "pin" and "thrum" types, and (2) the locus controlling Batesian mimetic polymorphism in Papilio memnon butterflies. For example, pin and thrum morphs of Primula have effects on genetic compatibility (pin style x thrum pollen, or thrum style x pin pollen matings are successful, while pin x pin, and thrum x thrum matings are rarely successful due to pollen-style incompatibility), and have different style length, anther height in the corolla tube, pollen size, and size on the stigma. Each of these effects is controlled by a different locus in the same supergene, but recombinants are occasionally found with traits combining those of "pin" and "thrum" morphs.

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