question

No it is not enough.

 

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.

The ABO blood type is controlled by a single gene with three alleles: i, I^A, and I^B. The I^A allele gives type A, I^B gives type B, and i gives type O. As both I^A and I^B are dominant over i, only ii people have type O blood. Individuals with I^AI^A or I^Ai have type A blood, and individuals with I^BI^B or I^Bi have type B.  A type A and a type B couple can also have a type O child if they are both heterozygous (I^Bi,I^Ai).

So in case of a heterozygous male with I^Ai genotype marrying a ii genotype female, the child has a probability of inheriting ii phenotype, which results in O blood group. The A blood group is actually dominant over O, but here we cannot determine the dominancy based on the given example.