In determining blood type,type A and type B are codominant to the recessive O type.If one parent had type A blood and one parent had type B blood,they could not have a child with type O blood.

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If both parents are heterozygous for the A and B alleles (genotype AB), they can pass on either the A or the B allele to their child, resulting in the child having either type A, type B, or type AB blood. However, if both parents are carriers of the recessive O allele (genotype AO or BO), they could pass on that allele to their child, resulting in the child having type O blood. Therefore, it is possible for two parents with type A and type B blood to have a child with type O blood.

In Determining Blood Type,type a and Type B Are Codominant