If a person has type A blood, what are their possible genotypes?

A person with type A blood can have two possible genotypes: AA or AO. This is because blood type is determined by the presence of specific antigens on the surface of red blood cells, which are influenced by two alleles inherited from each parent.

The genotype AA indicates that both alleles are of the A type, resulting in the expression of the A antigen on the red blood cells. The genotype AO represents a combination of one A allele and one O allele. The O allele does not produce any antigens and is considered recessive. In this case, the presence of the A allele is sufficient for the blood type to express as type A, even with an O allele present.

Thus, individuals can have either homozygous (AA) or heterozygous (AO) combinations for type A blood, which is why the answer is the first option. This understanding of blood type genetics is foundational in fields such as transfusion medicine and genetics.