supergene A segment of chromosome that is protected from crossing-over and so is transmitted intact from generation to generation, like a recon. The term is used to refer to several closely linked gene loci that affect a single trait or a series of inter-related traits, such as the genes coding for the expression of pin and thrum flower phenotypes in the primrose and other species of the genus Primula. Genes involved in the same biochemical function, e.g. those controlling the synthesis of tryptophan, are often clustered together in close linkage within the genome to form a supergene. The bacterial operon is one such example.
supergene A segment of chromosome that is protected from crossing-over and so is transmitted intact from generation to generation, like a recon. The term is used to refer to several closely linked gene loci that affect a single trait or series of interrelated traits, such as the set of gene loci controlling the colour and presence or absence of bands in the shell of the snail Cepaea nemoralis. Genes involved in the same biochemical function (e.g. those controlling the synthesis of tryptophan) are often clustered together in close linkage within the genome to form a supergene.
supergene A cluster of tightly linked genes that affect the same trait and are inherited apparently as a single unit. For example, supergenes are known to determine shell colour and patterning in terrestrial snails, and wing shape and colouring essential to mimicry in certain butterflies. This tight linkage is advantageous since it ensures that the appropriate combination of alleles for the character concerned is virtually always transmitted intact to the animal's offspring. Any rare recombinants will be selected against. A supergene can arise through inversion of part of a chromosome; crossing over within the inversion produces unbalanced recombinant chromatids, and hence zygotes containing these are nonviable. Thus, with respect to the inversion, only nonrecombinant zygotes are generally produced, giving a very low apparent rate of recombination between the loci in this region.
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