Question map
Father and mother having A and B blood group respectively
Explanation
The ABO blood group system is determined by three alleles: A, B, and O. Alleles A and B are codominant, while O is recessive [t2]. A person with blood group A can have the genotype AA or AO, and a person with blood group B can have the genotype BB or BO [t2]. If both parents are heterozygous (genotypes AO and BO), they each contribute one allele to their offspring [c3]. In this scenario, there is a 25% chance the child inherits the O allele from both parents, resulting in an OO genotype, which expresses as blood group O [t1][t2]. Therefore, parents with A and B blood groups can indeed give birth to a child with blood group O [t1]. Options 1 and 2 are incorrect because AB and O are both possible outcomes. Option 4 is incorrect as twins can share any blood group possible for that parental combination.
Sources
- [1] Science , class X (NCERT 2025 ed.) > Chapter 8: Heredity > 8.2.2 Rules for the Inheritance of Traits – Mendel's Contributions > p. 129