Which type of inheritance is responsible for skin colour in human beings ?

Polygenic inheritance .

The correct answer is Option (2) –Polygenic inheritance .

Polygenic inheritance involves the influence of multiple genes on a single phenotypic trait. Polygenic inheritance is an inheritance pattern controlled by three or more genes (multiple genes) and the graded phenotypes are due to the additive or cumulative effect of all the different genes of the trait. An example of human skin colour to understand the phenomenon of polygenic inheritance.

The term pleiotropy is derived from the Greek words pleio, which means "many," and tropic, which means "affecting." Genes that affect multiple, apparently unrelated, phenotypes are thus called pleiotropic genes . Pleiotropy should not be confused with polygenic traits, in which multiple genes converge to result in a single phenotype.

Co-dominance occurs when both alleles in a heterozygous individual contribute to the phenotype. In the case of the ABO blood group system, the I^A and I^B alleles are co-dominant. This means that if an individual has both I^A and I^B alleles (genotype I^AI^B), both alleles are expressed, and the individual has blood type AB, which has both A and B antigens on the surface of the red blood cells.