If a person with type O blood has a baby with a person who has type AB blood, then what blood type will the baby have?
The baby can be either type A or type B.
The parent with the O blood type can pass on only O alleles to the child. The parent with the AB blood type can pass on either an A allele or B allele. Therefore, the child's genotype would be heterozygous AO or BO, so the child will either have blood group A or B.