Answer:
Multiple alleles.
Step-by-step explanation:
Multiple alleles may be defined as the phenomena in which a particular trait or character is controlled by more than two genes. The multiple alleles do not follow the Mendelian inheritance.
The ABO blood group in humans explains the example of multiple allelism in which total 8 alleles is responsible for the expression of A, B, AB and O blood group. The multiple allelism is generally considered in case of population and rarely expressed by the individuals.
Thus, the answer is multiple allelism.