Genetics and blood types

Patient: Is it possible for a couple with A, B, or AB blood type to have a child with type O blood and how? Please explain how the blood type system works and how it is transmitted to the child?

Doctor: The test to determine your blood group is called ABO typing. Your blood sample is mixed with antibodies against type A a nd B blood, and the sample is checked to see whether or not the blood cells stick together. If blood cells stick together, it means the blood reacted with one of the antibodies.Only if the father or mother has A or B blood type, the child could have either A, B, O or AB blood type. On the other hand if one of the parents has AB blood type, the child would not be have O type by any means.