Gaucher disease (type I) is due to a defect in a gene that encodes a protein called acid (3-glucosidase. This enzyme plays a role in carbohydrate metabolism within the lysosome. The gene is located on the long arm of chromosome 1. People who inherit two defective copies of this gene exhibit Gaucher disease, the major symptoms of which include an enlarged spleen, bone lesions, and changes in skin pigmentation. Let's suppose a phenotypically unaffected woman, whose father had Gaucher disease, has a child with a phenotypically unaffected man, whose mother had Gaucher disease.
A. What is the probability that this child will have the disease?
B. What is the probability that this child will have two normal copies of this gene?
C. If this couple has five children, what is the probability that one of them will have Gaucher disease and four will be phenotypically unaffected?