Pleiotropism
- 1. Pleiotropism Harshraj Subhash Shinde KKW, CABT, NASHIK
- 2. Introduction • Defination- Pleiotropism is 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
- 3. Cont…. • Genes showing pleiotropy 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
- 4. 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"
- 5. Example • A classic example 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.
- 6. Cont… • Phenylalanine in the 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.