Q. ABO blood groups in humans are controlled by the gene I. It has three alleles–Iᴬ, Iᴮ 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
Explanation
[Solution from source] The six genotypes give four blood groups: A (IᴬIᴬ, Iᴬi), B (IᴮIᴮ, Iᴮi), AB (IᴬIᴮ, codominance) and O (ii). The answer 'three' misses the AB group, where both alleles are expressed. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.