Zoology - Principles of Inheritance and Variation Question with Solution | TestHub

A single gene can exhibit multiple phenotypic expressions. Such a gene is called a pleiotropic gene. An example of this is the disease phenylketonuria an autosomal recessive disorder, which occurs in humans. The disease is caused by a mutation in the gene that codes for the enzyme phenylalanine hydroxylase (single gene mutation). This manifests itself through phenotypic expression characterized by mental retardation and a reduction in hair and skin pigmentation.