Final answer:
Each diploid organism has two alleles for the ABO gene, which determines the ABO blood type, with three possible alleles (IA, IB, and i) in the population. IA and IB are codominant, while both dominate the i allele, allowing for six different genotypes.
Step-by-step explanation:
A diploid organism refers to any being that carries two sets of chromosomes—one from each parent—and thus two alleles for each gene. In the case of the ABO blood type, this means that each individual has two alleles for the ABO gene, with three possible alleles (IA, IB, and i) circulating in the population. A person with ABO blood type can have combinations such as IAIA, IAi, IBIB, IBi, or ii, leading to blood types A, B, AB, or O, respectively. It's important to note that while IA and IB are codominant alleles, both are dominant over the i allele. This creates an environment where six different genotypes can arise, contributing to the diversity in blood types observed in the human population.