Question

the letters in the following crosses represent parental blood types. which cross could produce offspring that represent all four blood types of the abo blood group?

Explanation:

Step1: Analyze $I^B I^B \times I^B I^B$

Offspring genotypes: $I^B I^B$ → Blood type: B only.

Step2: Analyze $I^A i \times I^B i$

Gametes from parent 1: $I^A, i$; Gametes from parent 2: $I^B, i$
Offspring genotypes: $I^A I^B$ (AB), $I^A i$ (A), $I^B i$ (B), $ii$ (O)

Step3: Analyze $ii \times I^A i$

Offspring genotypes: $I^A i$ (A), $ii$ (O) → Only 2 blood types.

Step4: Analyze $I^A I^A \times I^A I^B$

Offspring genotypes: $I^A I^A$ (A), $I^A I^B$ (AB) → Only 2 blood types.

Answer:

$I^A i \times I^B i$ (the purple cross option)