Question

An example of quantitative trait in man is
A. Hair colour
B. Colour of eye
C. Skin colour
D. Shape of nose

Answer 1

Hint: Trait is a distinguishing characteristic which typically differentiates a person. It is a genetically determined characteristic of a person. It can be both genotype and phenotype.

Complete Answer:
- A quantitative trait is a trait that can be described in a measurable quantity. These traits are controlled by many genes. It is also known as polygenic inheritance. In this the dominant genes have cumulative effect. An example of a quantitative trait is skin colour.
- The colour of the kin in human beings is determined by the quantity of melanin pigment present in the skin. It is determined by three pairs of genes present at different loci. Each dominant gene synthesizes a fixed amount of melanin.
- The hair colour is controlled by one gene which is brown/blonde gene. It consists of dominant brown and recessive blonde.
- Colour of eye is determined by a single gene where brown eyes are dominant over blue eyes.
- Shape of nose is controlled by a single trait dominant recessive gene.

Thus the correct answer is (C). An example of a quantitative trait in man is skin colour.

Note: Human skin colour is a multiple gene inheritance. It has a genotype with three dominant genes and three recessive genes. It leads to wide variation in traits. Height is also controlled by polygenes.