You are a cell biologist that is working with a genetic counselor. That means th
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Question
You are a cell biologist that is working with a genetic counselor. That means that you are the expert in the field of cell and molecular biology, while your colleague is the expert in genetics.
The two of you are working with a couple, the Johnsons, who are both carriers of the recessive mutant allele for Cystic Fibrosis (CF). That is, they have a ¼ chance of having a child with CF. Your partner, the genetic counselor, has already explained to them their chances of having a child with CF is ¼ and why. She has explained to them the symptoms of CF, which include lung infections and digestive problems. So, don’t discuss the genetics or symptoms of the disease.
What the Johnson’s want to know from you, is what causes the disease at the molecular level. It is your job to describe to them: 1. what molecule(s) are involved, 2. What does the mutation do to change the important protein in this process, 3. How does the mutant molecule affect the other cellular molecules – i.e. how does this mutation account for the symptoms of the disease.
The assignment is to write a “script” for what you would say to the Johnsons to explain the molecular cause of CF. Please write what you would say to them….this is different that what would be written (we talk differently than we write, so don’t copy webpages).
Explanation / Answer
1) The defective protein is called CFTR (Cystic fibrosis transmembrane conductance regulator)
2) This particular protein is mutated. The most common mutation is a deletion of three nucleotides that results in a loss of the amino acid phenylalanine (F) at the 508th position on the protein.
3) The normal CFTR protein is a chloride ion channel important in creating sweat, digestive juices and mucus. In the sweat ducts it facilitates the movement of chloride from the sweat duct into the cytoplasm. When the CFTR protein does not resorb ions in sweat ducts, chloride and thiocyanate released from sweat glands are trapped inside the ducts and pumped to the skin. Also hypothiocyanite, OSCN, cannot be produced by the immune defense system.. These are the net results of the mutant CFTR protein and this is how it harms the patient.
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