alleryThe ABO blood-group gene (I) has how many alleles in the human population?
A2 (one dominant, one recessive)
B4
C6
D3 (I^A, I^B, and i)
Answer & Solution
Correct answer: D. 3 (I^A, I^B, and i)
**Three alleles**: I^A, I^B, and i.
Since each person carries only two alleles, the ABO system gives **6 genotypes** (I^A I^A, I^A i, I^B I^B, I^B i, I^A I^B, ii) but only **4 phenotypes** (A, B, AB, O).
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