FIGURE 3-21 Inheritance Patterns (A) Recessive condition: If a parent has one mutant allele, the parent will not show symptoms of the disease but will be a carrier. If both parents carry a mutant allele, each of their offspring stands a 25 percent chance of developing the disease. (B) Dominant condition: A person with a single allele will develop the disease. If this person mates with a noncarrier, offspring have a 50-50 chance of developing the disease. If both parents are carriers, both will develop the disease, and offspring have a 75 percent chance of developing it.