Final answer:
The combination not possible among ABO blood types is an individual with type O blood from a mother with type A and a father with type AB since a type O individual must inherit the O allele from both parents.
Step-by-step explanation:
In the ABO blood types, the combination that is not possible is a. An individual with type O blood from a mother with type A and a father with type AB. This is because the child would receive one allele from each parent, and since type O is recessive, both parents would need to contribute an O allele.
Individuals with type O blood are known as universal donors because their red blood cells do not have A or B antigens, preventing an antibody reaction when their blood is given to others. On the other hand, those with type AB blood can receive any ABO type blood since they have neither anti-A nor anti-B antibodies in their plasma, making them universal recipients. The inheritance of ABO blood groups is determined by alleles, with A and B being codominant to each other and both dominant over O. Therefore, a type O individual, which is genotype OO, cannot be produced from a type A parent (genotype either AA or AO) and a type AB parent. By contrast, a type B individual can be produced by a type A and AB pairing, a type AB individual from a type B and AB pairing, and a type A individual from either two type A parents or a type O and AB pairing.