CBSE Class 10 Answered
This information is insufficient to determine the dominant blood group. During cross breeding, even recessive traits can express themselves phenotypically. For example, if a heterozygous male AO mates with OO female, then there is a probability of the child inheriting OO genotype. So, you cannot determine the dominant blood group in this case.
When a heterozygous AO male mates with OO female, the offspring could be either AO (i.e. with A blood group) or OO( i.e. with O blood group). Ideally if blood group A is present along with O, it is the dominating group, i,e, the person will show A blood group. But if we follow that principle in the above question, the child should be having A blood group and not O. So here the father has heterozygous blood group AO and the offspring gets the OO gene, resulting in O blood group. This does not mean that O is dominant over A group. It just means that recessive O gene is present in homozygous pattern.