Which genotype corresponds to blood type A?

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Multiple Choice

Which genotype corresponds to blood type A?

Explanation:
Blood type A arises when red blood cells have the A antigen on their surface. In the ABO system, the IA allele encodes the A antigen, while i has no A or B antigen. Because IA is dominant over i, any genotype that includes at least one IA allele will express the A antigen. That means IAIA and IAi both give the A phenotype. By contrast, IAIB would produce both A and B antigens (type AB), and ii would produce no antigens (type O). So the genotypes that correspond to blood type A are IAIA and IAi.

Blood type A arises when red blood cells have the A antigen on their surface. In the ABO system, the IA allele encodes the A antigen, while i has no A or B antigen. Because IA is dominant over i, any genotype that includes at least one IA allele will express the A antigen. That means IAIA and IAi both give the A phenotype. By contrast, IAIB would produce both A and B antigens (type AB), and ii would produce no antigens (type O). So the genotypes that correspond to blood type A are IAIA and IAi.

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