Multiple Alleles and ABO Grouping — NEET Biology
✅ Asked in NEET 2026What is the probability of children with O blood group when both parents are heterozygous for A and B blood groups respectively?
What is the probability of children with O blood group when both parents are heterozygous for A and B blood groups respectively?
Answer & NCERT explanation
Correct answer: A — 25%
Cross IAi x IBi gives offspring IAIB (AB), IAi (A), IBi (B), ii (O) in 1:1:1:1 ratio. So the probability of an O blood group child is 1/4 = 25%.
Read more NCERT concept on the PYQ
Do you realise that the example of ABO blood grouping also provides a good example of multiple alleles? Here you can see that there are more than two, i.e., three alleles, governing the same character. Since in an individual only two alleles can be present, multiple alleles can be found only when population studies are made.
NTA tests whether students understand that multiple alleles are alleles that exist in a population for one gene, but an individual can only carry two of them. The common trap is confusing multiple alleles with heterozygous genotypes—students think multiple alleles means one person has three blood types, which is wrong. In ABO, there are three alleles (I^A, I^B, i) in the population, but each person has only two alleles. Remember: multiple alleles are a population-level concept; individuals show the trait of only two alleles. This distinguishes populations from individuals, a key NEET principle.
What does NCERT say about Do you realise that?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.