Q.Define Pleiotropy.

Pleiotropy

Pleiotropy is the phenomenon in which a single gene influences two or more apparently unrelated phenotypic characters. Here one gene product (a protein/enzyme) affects several pathways, so a mutation in that single gene produces multiple, diverse effects.

A classic example is the gene for phenylketonuria, whose defect causes intellectual disability together with reduced hair and skin pigmentation. In sickle-cell anaemia, the single $\beta$-globin mutation affects red-cell shape, oxygen transport, spleen function and general health. In garden pea, one gene controls flower colour, seed-coat colour and axil pigmentation simultaneously.

Pleiotropy is distinct from:

• Polygenic inheritance — many genes control one trait.
• Codominance / incomplete dominance — allelic interactions at one locus.
• Independent assortment — a law describing gene transmission. …