Polymorphism (genetics)

Article By:

Slotman, Michel A. Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut.

Powell, Jeffrey R. Department of Biology, Yale University, New Haven, Connecticut.

Ford, Edmund B. Genetics Laboratory, Department of Zoology, Oxford University, United Kingdom.

Last reviewed:January 2021

DOI:https://doi.org/10.1036/1097-8542.535500

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• Polymorphism (genetics), published June 2014:Download PDF Get Adobe Acrobat Reader

A form of genetic variation, specifically, a discontinuous variation that occurs within plant and animal species in which distinct forms exist together in the same population, even the rarest of them being too common to be maintained solely by mutation. Polymorphism describes the situation in which there are one of two or more genotypic variants among members of a population. Variation at a single base pair in a sequence of deoxyribonucleic acid (DNA), termed a single-nucleotide polymorphism (SNP), is the most prevalent form of polymorphism (Fig. 1). Human blood groups are examples of polymorphism. In contrast, the diversity of height among humans is not an example of polymorphism because height varies along a continuum and does not fall into distinct tall, medium, and short types. See also: Blood group; Deoxyribonucleic acid (DNA); Genetics; Genomics; Human genetics; Human genome; Mutation

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