Dominant Inheritance When a parent has a one, defective dominant gene (D), which suppresses its normal counterpart (d), affecting that parent. If affected parent mates with an unaffected and non-carrier partner (dd), their offspring are either not affected or affected, but they will not be carriers.

Recessive Inheritance When both parents are carriers who are not affected by the defective gene, they both carry a normal gene (N), and a defective, recessive gene (n). Their offspring are either carriers, not affected or not affected.