Parents with the genotypes ao and ab have a child. what are all the possible blood types of the child? a, b o, ab a, ab, b o, ab, a

A, AO, AB and B.    

Explanation:

ABO blood group is as case of codominance inheritance pattern. The human blood group is determined by a gene I. it has two alleles IA and IB.  Its recessive allele is IO. A person having IAIA (homozygous) or IAIO (heterozygous) will have blood group A. If a person having IBIB or IBIO will have blood group B. It both the alleles IA and IB are present, then both genes are express completely resulting into a new phenotype have blood group AB. If a person having IOIO, then blood group is O.  

In the given question a parent have blood groups AO and AB.  They will produce gametes A, O and A, B. According to Mendel’s pattern of inheritance, the possible blood type of child will be A, AO, AB and B.