Q.Which one of the following is an example of polygenic inheritance ?

Human skin colour, controlled additively by several genes to give a continuous range of shades, is the classic example of polygenic inheritance among the options given.

Working

Polygenic inheritance occurs when a single phenotypic trait is controlled not by one gene but by several genes acting together, each contributing a small, additive effect, so that the trait shows continuous (quantitative) variation across a whole range of intermediate phenotypes rather than a few discrete classes -- the population distribution for such a trait typically approximates a bell (normal) curve. Human skin colour is the standard textbook illustration: multiple gene pairs (classically estimated as 3 or 4) each add or subtract pigment (melanin) in an additive fashion, producing the wide, continuous spectrum of human skin shades seen across populations.

By contrast:

• Pod shape in garden pea (inflated dominant over constricted) is a simple monohybrid (single-gene) Mendelian trait, not polygenic. …