certain traits that are under the control of more than 2 alleles
ABO blood groups
three alleles for the antigen on blood cells
the Ia alleles produce A type antigens
the Ib alleles produce B type antigens
the io allele codes for the production of no antigens (recessive)
incomplete dominance
the action of one allele ones not completely mask the action of the other and neither allele has dominant control over the trait. the heterozygous offspring is intermediate in phenotype and shows a blennding of features
