Question

ABO blood groups in humans are controlled by the gene l. It has three alleles, I${}^A$, I${}^B$ and I. Since, there are three different alleles, six different genotypes are possible. How many phenotypes can occur?

• A. Two
• B. Three
• C. One
• D. Four

Answer 1

Answer: (D)

Four

Six different possible genotypes are:

I${}^A$I${}^B$, I${}^A$I, I${}^B$I, I${}^A$I${}^A$, I${}^B$I${}^B$, II,
and the possible number of phenotypes for ABO blood group is 4:

1. Blood group A (I${}^A$I${}^A$, I${}^A$I)
2. Blood group B (I${}^B$I${}^B$, I${}^B$I)
3. Blood group AB (I${}^A$I${}^B$)
4. Blood group O (II)

Thus, the correct answer is option D.