Cystic fibrosis is an exceedingly rare autosomal recessive disorder. A man and woman are planning on having a child. The potential father has a brother who has cystic fibrosis. It is not known if the potential father is a carrier. If the male and female have one child, what is the probability that they will have a daughter with cystic fibrosis?

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Jarrod RobelLv2

18 Apr 2018

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Cystic fibrosis is inherited as an autosomal recessive. Twoparents without cystic fibrosis have two children with cysticfibrosis and three children without. The parents come to you forgenetic counseling.
1. What is the probability that their next child will have cysticfibrosis?
2. Their unaffected children are concerned about beingcarriers. What is the probability that a
  
  given unaffected child in this family is a carrier?

amberbeaver601

1) You have been hired as a genetic counselor. Your first patient is a young woman named Lei who comes to you because her brother has cystic fibrosis. (Learn more about this disease in the PowerPoint slides â find out how it is inherited, is it dominant or recessive?) Lei is healthy but would like to know the risk that she is a carrier for the disease. Both her parents are healthy as is her older sister. a. Fill in the Punnett Square below with her parentâs genotypes to predict her risk of being a carrier of cystic fibrosis. You should be able to determine her parentâs genotypes from information given above. Male/ Female b. Explain to Lei her risk of being a carrier: 2). A blood DNA test for the cystic fibrosis allele becomes available and you recommend to Lei that she take the blood test and that her FiancÃ© Robert take the test as well. Leiâs test shows that she is a carrier. Robert is not. What is the risk that their future child will have cystic fibrosis? a. Use the Punnett Square below to predict Lei and Robertâs risk of having a child with CF? Male/ Female b. Write down your explanation to Lei and her FiancÃ©: 3. Another patient, Mark, comes to you because his father has just been diagnosed with the rare genetic disorder known as Huntingtonâs disease. Mark would like to know his potential risk of developing the disease (you must read about the inheritance pattern of Huntingtonâs disease in the Lecture and online games to answer this correctly!). Assume that his mother is showing no signs of Huntingtonâs disease. a. Fill in the Punnett Square below to predict Markâs risk of getting Huntingtonâs disease. Male/ Female b. Your explanation to Mark:

During a work-up for infertility, Brad (32 years old) is found tohave azospermia caused by congenital bilateral absence of the vasdeferens (CBAVD). His physician explains that 75-80% of men withCBAVD have a mutation in both cystic fibrosis transmembraneconductance regulator (CFTR) genes. The physician recommends thatBrad have CFTR genetic testing. Brad (a pediatric nurse) questionshis physician's medical acumen, exclaiming that he has absolutelyno pulmonary or pancreatic symptoms common with cystic fibrosis nordoes he have any family history of the disease. The physicianexplains that although mutations in CFTR are most often associatedwith pulmonary disease and pancreatic insufficiency, some men withtwo mutations have no symptoms other than CBAVD. Brad is laterdiagnosed with cystic fibrosis when he is found to carry an IVS8-5Tmutation in one CFTR gene and a P499A mutation in the other CFTRgene.

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

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

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

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

a) Polymorphisms

b) Alleles

c) Markers

d) Autosomes

5. Because Brad carries two different CFTR mutations, it would beappropriate 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 theIVS8-5T / P499A mutations as the (genotype / phenotype).

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

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

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

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