Explain pleiotropy with reference to phenylketonuria.

Explanation

Pleiotropy occurs when one gene influences two or more unrelated phenotypic effects. (Pleo means many and tropism means effect) A mutation in a pleiotropic gene may have an effect on several traits simultaneously due to the gene coding for a product used by a myriad of cells or different targets that have the same signaling function.

Phenotype Phenylketonuria : (i) Enzyme deficiency is due to abnormal autosomal recessive gene on chromosome 12. (ii) It is inborn metabolic disorder. (iii) Phenylketonuria is a condition caused due to deficiency of phenylalanine hydroxylase enzyme (iv) When this enzyme is missing, the body is unable to break down phenyl alanine. (v) Heterozygous individuals are normal but they are the carriers. (vi) Disease is expressed in homozygous. (vii) Symptoms are : mental retardation, decreased pigmentation of skin, loss of hairs, eczema, its increase in body is very dangerous.