Which parental genotypes cannot produce a blood group O child in NEET 2026?
Option D cannot. A type O child must have genotype ii. Both parents must therefore supply one i allele each. The father with IAIB has no i allele to give, so ii cannot form.
The question required students to identify which of the four listed parental genotype pairs cannot produce such a child. The child has blood group O therefore genotype must be ii. The options involve heterozygous and homozygous dominant combinations for IA, IB and i alleles.
Option A: IAi × IBi
Option B: IAi × IAi
Option C: IBi × IBi
Option D: IAIB × IAi
What is the step-by-step official solution for the NEET 2026 ABO blood group question?
Blood group O requires genotype ii, hence both parents must each contribute one i allele. Option D is the pair that cannot produce the child.
Option A (IAi × IBi): both parents carry i → ii child possible.
Option B (IAi × IAi): both parents carry i → ii child possible.
Option C (IBi × IBi): both parents carry i → ii child possible.
Option D (IAIB × IAi): father has no i allele and can give only IA or IB → ii child impossible.
Therefore correct choice is D. This allele-contribution check reaches the answer in under 60 seconds.
Why do students wrongly eliminate option B in ABO blood group questions?
Students often mark option B (IAi × IAi) as impossible because they treat it only as “both parents have A allele so child must be A” without separating the segregation of the i allele from each parent.
The precise procedural error is forgetting to verify independent contribution of the recessive i from each parent before eliminating. Each parent produces gametes IA and i in equal ratio. The cross therefore yields one quarter ii offspring.
The 25 percent probability of ii is ignored when the student focuses only on the dominant phenotype. The official method demands a separate check for i availability in both parents.
What exact rules of ABO inheritance does the official solution apply?
IA and IB are codominant to each other and both completely dominant over i. Blood group O can only be ii (homozygous recessive). Each parent contributes exactly one allele to the child. A parent without an i allele (IAIA, IBIB or IAIB) cannot help form ii.
These four statements solve every “impossible parent” question.
Can both AB parents produce a blood group O child?
No. Both parents are IAIB. Neither carries an i allele. The child must receive one allele from each parent and will therefore be either IAIA, IAIB or IBIB. Genotype ii is impossible.
A couple with blood groups A (IAi) and B (IBi) can produce all four blood groups: A, B, AB and O. The genotype that gives O is ii, formed when both parents contribute i.
For a child with blood group AB, the parental pair ii (O) and IAIA (A) is impossible. The second parent lacks any IB allele so the child cannot receive both IA and IB.
How can you solve any ABO inheritance MCQ in 45 seconds for NEET 2026?
Write child genotype first (ii for O). Scan every option for presence of at least one i in BOTH parents. Eliminate the option where even one parent lacks i. Never draw full Punnett square in exam; allele availability check is enough.
This template comes directly from the official method. Search the past-paper archive by chapter to find every previous Genetics and Evolution MCQ that tested the same allele-contribution logic.
How does mastering this ABO blood group question help in NEET 2026?
Biology carries 360 marks out of 720. Genetics and Evolution is high weightage. NEET 2026 was held on 2026-06-21 after the original 2026-05-03 sitting was cancelled.
Apply the “both parents must supply i” filter to every inheritance question in remaining mocks. For any similar question you get stuck on during those mocks, use the photograph-a-doubt tool.
Next step: photograph a doubt on NEET JEEnius AI and photograph any question you are stuck on and get a step-by-step solution across Physics, Chemistry and Biology (20 free a month).
Keep going with Lens and Mirror Combination NEET 2025: Object at R/(2μ-1).
Frequently asked questions
Which parental genotypes cannot produce a blood group O child in NEET 2026?
The pair IAIB × IAi cannot produce a blood group O child. The IAIB parent has no i allele to give, making genotype ii impossible. Options A, B and C all allow both parents to contribute i.
Why do students wrongly eliminate option B in ABO blood group questions?
Students treat IAi × IAi as only producing A blood group and ignore the i allele. Each parent produces IA and i gametes in 1:1 ratio. This gives 1/4 probability of ii offspring with blood group O.
Can both AB parents produce a blood group O child?
No. Both AB parents are IAIB and lack any i allele. The child must receive one allele from each and will always have IA or IB, making ii genotype impossible. A and B heterozygous parents can produce O.
How can you solve any ABO inheritance MCQ in 45 seconds for NEET 2026?
Write the child genotype first, such as ii for O. Check whether both parents in each option carry at least one i allele. Eliminate any option where even one parent lacks i. No Punnett square is needed.