Answer :
Six phenotypes are possible in a one gene/three
allele system that displays codominance to each other with three alleles, a1, a2, a3.
3 homozygous and 3 heterozygous
combinations. Each unique combination of two alleles results in a distinct
phenotype. Possible combinations are:
a1/a1
a1/a2
a1/a3
a2/a2
a2/a3
a3/a3