Blood Type Inheritance: Can O+ and A Blood Type Parents Have an AB- Child?

No, a father with type O pos and a mother with type A cannot produce a child with type AB negative blood.

The AB blood type is formed when an A allele and a B allele are inherited from both parents. The O blood type is formed when two o alleles are inherited, and the negative Rh factor is inherited when two negative Rh alleles are inherited.

For a child to have type AB negative blood, both parents would have to carry both the A and B alleles, as well as the negative Rh allele. However since one parent has OO phenotype, it is not possible for them to produce child of AB blood group.