Recessive and Dominant Inheritance
Mechanisms of recessive and dominant inheritance.
Both parents carry a normal gene (N), and a faulty, recessive,
gene (n). The parents, although carriers, are unaffected by the faulty
gene. Their offspring are affected, not affected, or carriers. This type
of inheritance was first shown by Mendel.
One parent has a single, faulty dominant gene (D), which overpowers
its normal counterpart (d), affecting that parent. When the affected
parent mates with an unaffected and non-carrier mate (dd), the offspring
are either affected or not affected, but they are not carriers.