NEET 2026 (Phase 1) · BiologyPrevious Year Question
What is the probability of having children with ‘O’ blood group, where both mother and father are heterozygous for ‘A’ and ‘B’ blood group, respectively?
- A.25%✓
- B.0%
- C.75%
- D.50%
Correct Answer
(A) 25%
Solution & Explanation
Answer: (a) 25% Solution: A heterozygous A parent is I^Ai and a heterozygous B parent is I^Bi. The cross I^Ai x I^Bi gives I^AI^B (AB), I^Ai (A), I^Bi (B) and ii (O) in 1:1:1:1 ratio. Only the ii offspring is O group, i.e. 1/4 = 25%. NCERT: Ch 15, p.195, line 22 — "ABO grouping is based on the presence or absence of two surface antigens"
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