Question

A polygenic inheritance in human beings is

• A. Skin colour
• B. Sickle cell anaemia
• C. Colour blindness
• D. Phenylketonuria

Answer 1

The correct option is A Skin colour

A polygenic trait is the one that is governed by more than one gene. Human skin colour is a polygenic trait governed by more than one gene, where dominant allele of each gene express only a part of trait and the full trait is expressed only in the presence of dominant alleles of all multiple genes. It is called as polygenic inheritance. These genes control skin pigmentation only, no other phenotypic trait is affected by these genes. This makes option A correct.

Sickle cell anaemia is the autosomal recessive disorder that is governed by two alleles of the single gene ($H{b}^b$ and $H{b}^s$), which makes option B wrong.

Colour blindness is an X-linked recessive disorder, which is governed by the single gene (X${}^c$) which makes option C wrong.

Phenylketonuria is an autosomal recessive disorder, which is also governed by a single gene.