Polygenic Inheritance : In this, traits are controlled by three or more genes (multiple genes). These traits are called polygenic traits. The phenomenon shows participation of each allele and is also influenced by the environment and is called quantitative inheritance as the character/phenotype can be quantified. For example, human skin colour which is caused by a pigment melanin. The quantity of melanin is due to three pairs of polygenes (A, B and C). If a black or very dark (AABBCC) and white or very light (aabbcc) individuals marry each othe1, the offsprings show intermediate colour also called mulatto (AaBbCc).
Multiple Alleles: When more than two alternative forms (allele) of a gene occupy the same locus on a chromosome in a population, these are known as multiple alleles. The ABO blood grouping is a good example of multiple alleles. In this case, more than two, i.e. three alleles are present governing the same character.
