Question

In the human ABO blood group system, the alleles A and B are dominant to O, what will be the number of different possible genotypes?

• A. 4
• B. 8
• C. 6
• D. 12

Hint:

3 alleles $\rightarrow$ 6 genotypes, 4 phenotypes (A, B, AB, O).

Answer 1

The Correct Option is C

Step 1: Concept
The ABO system is a multiple allele system with three alleles: $I^A$, $I^B$, and $i$.

Step 2: Meaning
Genotypes are the possible combinations of these three alleles taken two at a time.

Step 3: Analysis
The possible combinations are: 1. $I^A I^A$ 2. $I^A i$ 3. $I^B I^B$ 4. $I^B i$ 5. $I^A I^B$ 6. $ii$ Formula: $n(n+1)/2$, where $n=3$ alleles $\rightarrow 3(4)/2 = 6$.

Step 4: Conclusion
There are 6 distinct genotypes in the ABO blood group system. Final Answer: (C)