A child with blood group genotype different from those of both parents and with a mother of genotype OO, can only have a father of genotype
Answer Details
If a child has a blood group genotype that is different from both parents and the mother has a genotype of OO, it means that the child must have inherited an allele from the father that is different from O. Since the mother's genotype is OO, she can only contribute an O allele to the child. This means that the father must have contributed either an A, B or AB allele to the child, since these are the only other possible blood group alleles. Therefore, the father of the child can only have a genotype of either A, B, or AB.