During a work-up for infertility, Brad (32 years old) is found to have azospermia caused by congenital bilateral absence of the vas deferens (CBAVD). His physician explains that 75-80% of men with CBAVD have a mutation in both cystic fibrosis transmembrane conductance regulator (CFTR) genes. The physician recommends that Brad have CFTR genetic testing. Brad (a pediatric nurse) questions his physician's medical acumen, exclaiming that he has absolutely no pulmonary or pancreatic symptoms common with cystic fibrosis nor does he have any family history of the disease. The physician explains that although mutations in CFTR are most often associated with pulmonary disease and pancreatic insufficiency, some men with two mutations have no symptoms other than CBAVD. Brad is later diagnosed with cystic fibrosis when he is found to carry an IVS8-5T mutation in one CFTR gene and a P499A mutation in the other CFTR gene.

1. Do you agree with the "diagnosis" of cystic fibrosis? Explain your answer.

2. What impact might this diagnosis have on his ability to obtain life, health, &/or disability insurance?

3. Explain how it is possible that Brad has two mutated CFTR genes when no one else in his family has cystic fibrosis.

4. Brad's CFTR genes, altered by mutations are called: (choose the best answer)

a) Polymorphisms

b) Alleles

c) Markers

d) Autosomes

5. Because Brad carries two different CFTR mutations, it would be appropriate to say he is:

(Choose the best answer and explain your choice.)

a) Homozygous for the CFTR mutations

b) Hemizygous for the CFTR mutations

c) Heterozygous carrier for the CFTR mutations

d) Compound heterozygous for the CFTR mutations

6. The CBAVD is referred to as the (genotype / phenotype) and the IVS8-5T / P499A mutations as the (genotype / phenotype).

With the technique, microscopic epididymal sperm aspiration (MESA), Brad may be able to produce biological children. Assuming that Brad's wife is not a carrier of a CFTR mutation:

7. What is their risk for having a child with cystic fibrosis?

8. What are their chances for having a child that is a carrier of one of Brad's CFTR mutations?

9. If Brad's wife is found to be a carrier of one of the 1000 possible CFTR mutations, what is their chance of having a child with cystic fibrosis?