Pleiotropy: One Gene Can Affect Multiple Traits - Nature

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A conceptual diagram shows how a single gene may influence three separate traits. The term gene X is shown in black letters inside of a white rectangular box with a black outline. Three black arrows emanate from the center of the right edge of the rectangular box containing the term gene X. The first arrow extends upward to the right at a 45-degree angle and terminates in another white rectangular box with a black outline that contains the term trait 1 shown in black letters. The second arrow extends to the right in a straight line that terminates in another white rectangular box with a black outline that contains the term trait 2 shown in black letters. The third arrow extends downward to the right at a 45-degree angle and terminates in another white rectangular box with a black outline that contains the term trait 3 shown in black letters.Figure 1: Diagram of pleiotropy.A pleiotropic gene is a single gene that controls more than one trait.© 2008 Nature Education All rights reserved. View Terms of UseDuring his study of inheritance in pea plants, Gregor Mendel made several interesting observations regarding the color of various plant components. Specifically, Mendel noticed that plants with colored seed coats always had colored flowers and colored leaf axils. (Axils are the parts of the plant that attach leaves to stems.) Mendel also observed that pea plants with colorless seed coats always had white flowers and no pigmentation on their axils. In other words, in Mendel's pea plants, seed coat color was always associated with specific flower and axil colors.

Today, we know that Mendel's observations were the result of pleiotropy, or the phenomenon in which a single gene contributes to multiple phenotypic traits. In this case, the seed coat color gene, denoted a, was not only responsible for seed coat color, but also for flower and axil pigmentation (Fairbanks & Rytting, 2001).

The term pleiotropy is derived from the Greek words pleio, which means "many," and tropic, which means "affecting." Genes that affect multiple, apparently unrelated, phenotypes are thus called pleiotropic genes (Figure 1). Pleiotropy should not be confused with polygenic traits, in which multiple genes converge to result in a single phenotype.

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