(a) What is polygenic inheritance ? Explain with the help of a suitable example.

(b) How are pleiotropy and Mendelian pattern of inheritance different from polygenic pattern of inheritance ? [5]

(a) Polygenic Inheritance : Polygenic inheritance occurs when one characteristic is controlled by two or more genes whose expression is due to the cumulative effect of the dominant genes that are present together. [0.5+0.5]

More the number of dominant genes, the expression of the trait will be more distinct, more the number of recessive allelles, the trait will be diluted, if number of dominant and recessive
allelles are equal the effect is intermediate . [1]

Examples : Human skin color, Human height (any one ) [1]

(b)Mendelian inheritance refers to the expression of inheritance of monogenic traits, that is traits that are controlled by one gene. [1]

Pleiotropy refers to one gene influencing many traits. [1]