Question

1. codominance occurs when both alleles are dominant. which of the genotypes results in a codominant blood type?
2. in a person with the i^a i genotype, which allele is dominant, i^a or i?

Explanation:

For Question 2:

Step1: Recall blood type genetics

In blood type genetics, the alleles \( I^A \), \( I^B \), and \( i \) are involved. The \( I^A \) and \( I^B \) alleles are codominant, and both are dominant over \( i \). For a genotype \( I^A i \), we compare the dominance of \( I^A \) and \( i \).

Step2: Determine dominant allele

Since \( I^A \) is dominant over \( i \) (as \( i \) is recessive and \( I^A \) leads to A - type antigen expression), in the \( I^A i \) genotype, the \( I^A \) allele is dominant.

Codominance in blood types requires both dominant alleles (\( I^A \) and \( I^B \)) to be expressed. The genotype \( I^A I^B \) has both alleles, leading to AB blood type (codominant).

Answer:

\( I^A \)

For Question 3:

To determine the genotype with codominant blood type, we know that in blood type genetics, codominance is seen when both \( I^A \) and \( I^B \) alleles are present (genotype \( I^A I^B \)). This is because both alleles are expressed, leading to the AB blood type where both A and B antigens are present on the red blood cells, showing codominance. Other genotypes like \( I^A I^A \), \( I^A i \) show dominance of \( I^A \) over \( i \) (not codominance), \( I^B I^B \), \( I^B i \) show dominance of \( I^B \) over \( i \), and \( ii \) is recessive (O blood type). So the genotype \( I^A I^B \) results in a codominant blood type (AB blood type).