Pleiotropism

Pleiotropism

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  Pleiotropism Harshraj Subhash Shinde KKW,CABT, NASHIK
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  Introduction • Defination- Pleiotropismis defined as when one gene influences multiple, unrelated phenotypic traits • Pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits • Mutation in a pleiotropic gene may have an effect on some or all traits • Mechanism of pleiotropy in most cases is the effect of a gene on metabolic pathways that contribute to different phenotypes
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  Cont…. • Genes showingpleiotropy produce a single polypeptide just like other non pleiotropic genes • But their polypeptide governs such a biochemical reaction, which is basic to many developmental events. • As a result impairment of the function
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  History • The term"pleiotropie" was coined in a 1910 by Festschrift • The term pleiotropy comes from the Greek πλείων pleion, meaning "more", and τρόπος tropos, meaning “character"
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  Example • A classicexample of pleiotropy is the human disease phenylketonuria (PKU). • This disease can cause mental retardation and reduced hair and skin pigmentation, • phenylketonuria is due to mutation in a single gene that codes for the enzyme phenylalanine hydroxylase • Phenylalanine hydroxylase converts the amino acid phenylalanine to tyrosine • Due to mutation, conversion of phenylalanine to tyrosine is reduced or ceases entirely.
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  Cont… • Phenylalanine inthe bloodstream is toxic to the developing nervous system of newborn and infant children and which causes mental retardation. • Where as tyrosine is used by the body to make melanin (an important component of the pigment found in hair and skin) • The failure to convert normal levels of phenylalanine to tyrosine results in less pigmentation of hair and skin.