Match the Column I with Column II .

a-2, b-3, c-4, d-1

The correct answer is Option (4) –a-2, b-3, c-4, d-1

Thalassemia : This is also an autosome-linked recessive blood disease  transmitted from parents to the offspring when both the partners are unaffected carrier for the gene (or heterozygous).

Pleiotropy: When  a single gene can exhibit multiple phenotypic expression. Such a gene is called a pleiotropic gene. The underlying mechanism of pleiotropy in most cases is the effect of a gene on metabolic pathways which contribute towards different phenotypes. An example of this is the disease phenylketonuria, which occurs in humans. The disease is caused by mutation in the gene that codes for the enzyme phenyl alanine hydroxylase (single gene mutation).

Polygenic inheritance : When traits are gnerally controlled by three or more genes and are thus called as polygenic traits. Besides the involvement of multiple genes polygenic inheritance also takes into account the influence of environment. Human skin colour is another classic example for this.

Haemophilia: This sex linked recessive disease, which shows its transmission from unaffected carrier female to some of the male progeny. In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected.