Question
For a person with blood group ‘O’, which of the following is not a possible combination of parents' blood group genotypes ?
NEET
Zoology
Principles of Inheritance and Variation
2026
NEET 2026 (Re-NEET)
NEET Zoology Question (2026) — Solution
Options
- A. Father : I^A I^B and Mother : I^A i
- B. Father : I^A i and Mother : I^B i
- C. Father : I^A i and Mother : I^A i
- D. Father : I^B i and Mother : I^B i
Answer
A. Father : I^A I^B and Mother : I^A i
Step-by-step solution
Blood group 'O' corresponds to the homozygous recessive genotype ii. For a child to have blood group 'O', they must inherit one i allele from each parent. This means both parents must possess at least one i allele in their genotype. In the combination Father : I^A I^B and Mother : I^A i, the father does not have an i allele. Therefore, he can only pass either an I^A or an I^B allele to the offspring. As a result, it is impossible for this couple to produce a child with the ii genotype (blood group 'O'). In all other given combinations, both parents are heterozygous and possess an i allele, making it possible for them to have a child with blood group 'O'. Answer: Father : I^A I^B and Mother : I^A i
Related: Zoology — Principles of Inheritance and Variation · All PYQ Banks