[Campbell Biology P.329] Based on Figure 14.11 b , what are the dominance relationships amon... | Practice Question

Based on Figure 14.11 b , what are the dominance relationships among the IA, IB, and i alleles for the ABO blood groups?

  • A: IA and IB are both dominant over i, and IA and IB are codominant.
  • B: IA is dominant over IB, and both are dominant over i.
  • C: i is dominant over IA and IB.
  • D: All three alleles are codominant.

Explanation

Figure 14.11 b shows that genotypes IAIA and IAi both result in phenotype A, and IBIB and IBi both result in phenotype B, indicating that IA and IB are dominant over i. The genotype IAIB results in phenotype AB, where both A and B carbohydrates are present, demonstrating codominance between IA and IB.