As stated, the alleles A and B are codominant to allele O. This means that the individual will not have the O blood type when it is accompanied by the other alleles. But also, since this is a recessive allele, a pair could have an offspring with the blood type O even if none of these individuals have it.
A, B, ad O blood type in humans is controlled by a single gene with three alleles: IA (or A), IB (orB), and i (or O). Type O is the recessive trait. The i (O) allele is recessive to both IA (or A), and IB (orB). Which of the following could be possible genotypes of the parents ofa person with type O blood?
A. IAi (AO) and IAIA (AA)
B. IAi (AO) and IBi (BO)
C. IAIB (AB) and IAi (AO)
D. IAIB (AB) and ii (OO)
E. All of the above are possible