Question

Example of quantitative inheritance is
A. Colour of skin
B. Colourblindness
C. Klinefelter’s syndrome
D. Alkaptonuria

Answer 1

Hint: Quantitative inheritance refers to a trait that is determined by more than one gene. These are called polygenes. Thus, polygenic inheritance shows quantitative inheritance. Each allelic pair of a polygenic has a specific quantitative effect on the phenotype of progeny. It is associated with the largest organ of the body.

Complete answer: A quantitative inheritance is defined as the function of polygenes. The colour of the skin shows polygenic inheritance, which means that the skin colour is determined by more than one gene. These genes are A, B, and C. Each of these polygenes shows a particular quantitative effect in the physical character, i.e., the skin colour of the progeny. So, the progeny shows a combined result of different alleles. Another example of quantitative inheritance is height. It is also controlled by polygenes. Thus, height, weight, skin colour, intelligence, etc. are all quantitative inheritance traits. Characters determined by polygenic or quantitative genes are called polygenic characters. Galton in 1883 predicted the quantitative characters in humans. The more the number of dominant alleles, the more prominent will be the expression of character.
a) Colorblindness is a condition caused by the inheritance of X-linked recessive traits located on the X-chromosome.
b) Klinefelter’s syndrome is a genetic disease caused due to abnormal sex chromosome numbers. The affected individual carries 47 chromosomes instead of 46 which is a normal chromosome count.
c) Alkaptonuria is also a disorder. It is a metabolic disorder caused by the deficiency of an oxidase enzyme. This enzyme is required for the breakdown of homogentisic acid.
So, the right answer is option A.

Note: It is believed that polygenes arrived from evolution. During evolution, the duplication of chromosome parts occurred that resulted in the formation of multiple copies of the same gene. Mendel, who is the father of genetics, was popular to study qualitative inheritance.