If both parents have type O blood, what is the probability that their children will also have type O blood?

To understand why the probability that children of two type O blood parents will also have type O blood is 100%, it is essential to consider the genetic inheritance patterns of blood types.

Human blood type is determined by the ABO blood group system, which includes three alleles: A, B, and O. Each person inherits one allele from each parent. The A and B alleles are both dominant, whereas the O allele is recessive. This means that a person with type O blood has two O alleles (genotype OO), as O is recessive and requires both inherited alleles to be O for this blood type to be expressed.

When both parents have type O blood, their genotypes can only be OO. When these two parents have children, each child can only inherit one O allele from each parent. Therefore, the genetic combination for every child would be OO.

This results in all children having type O blood, leading to a probability of 100% that children from two type O parents will also have type O blood. This is a clear illustration of a simple Mendelian inheritance pattern where both parents contribute the recessive alleles exclusively, resulting in offspring that exhibit the same recessive trait.