Extensions of Mendelian Genetics (Deviation from Mendelism) - Intragenic Interactions - Pleiotropy

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Notes

Pleiotropy - A single gene affects multiple traits:

  • In Pleiotropy, a single gene affects multiple traits and alters the phenotype of the organism.
  • The Pleiotropic gene influences a number of characters simultaneously and such genes are called pleiotropic genes were crossed with a variety of peas having white flowers, light coloured seeds and no spot on the axils of the leaves, the three traits for flower colour, seed colour and a leaf axil spot all were inherited together as a single unit.
  • Example - sickle cell anemia.
  • The underlying mechanism of pleiotropy in most cases is the effect of a gene on metabolic pathways which contribute towards different phenotypes, for example, disease phenylketonuria.
  • This disease is caused by a mutation in the gene that codes for the enzyme phenylalanine hydroxylase (single gene mutation).
  • The mutation in gene is exhibited through phenotypic expression characterised by mental retardation and reduction in pigmentation of hair and skin.
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