a. How many of the nucleotides present in the mRNA strand (at the ribosomes) are required to code for these amino acids?
b. Most mutations (70%) in patients with cystic fibrosis are due to a deletion of 3 nucleotides (see diagram). Amino acid number 508 is lost. This mutation is known as AF508 (pronounced delta F508 - delta indicates a deletion).
i. What amino acid is lost due to this deletion?ii. Why is it called F508 - why "F" (see the genetic code in your book)?
iii. What is amino acid 507 in this sequence?
iv. Why is amino acid 507 the same in both sequences? Explain.
v. Does this deletion result in a "frame-shift'' mutation? Explain.
vi. What would the impact be if only 1 or 2 nucleotides had been deleted? Do you think this would have a greater or lesser impact on the resulting protein?
2. Cystic fibrosis (CF) is a genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. CF is inheritance. It is caused by the presence of mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. A normal couple intends to have children but consult a genetic counselor because the man has a sister with CF and the woman has a brother with CF. There are no other known cases in their family. They want to know:
(1) What is the probability that their first child would be normal?
(2) What is the probability that their first two children would have CF?
(3) If they would like to have five children, what is the probability that at least two of them would be normal?
3. Cystic fibrosis (CF) is a genetic disease caused by a mutation in the CFTR gene. One of the distinguishing features is the thick mucus that lines both the airways and the intestinal tract of affected individuals. One of the mutations associated with CF is related to a chloride ion transporter. In healthy individuals, the chloride channels open periodically to allow the cell to maintain a normal balance of chloride ions between the inside and outside of the cell. In CF individuals, these chloride channels do not function, and chloride ions build up inside the cell.
a. Explain using the concept of water potential why the misfolding of the ion channel CFTR leads to thick mucus lining the tissues of the lungs and intestines.
b. Describe the mechanism of cell communication involved as seen in the diagram. A new drug to treat a particular type of CFTR is a modified protein. Describe two considerations for protein engineers to keep consistent to ensure proper functioning of the protein.
4. Sarah and Michael elected to have Sarah's DNA further analyzed. A week later they met again with the genetic counselor to discuss the test result. "So do I have a mutation in my CF gene?” asked Sarah. 'Yes,” the genetic counselor replied. “You have a rare allele called V232D. This mutation affects the folding of the CFTR protein. Because they don’t fold correctly proteins expressed from the V232D allele are not stable and usually do not make functional channels at the cell membrane.”
In their first experiment, the authors looked at expression of the CFTR protein expressed from the wild type (CFTR) or mutant (CFTR V232D) alleles in HEK-293 human kidney cells using a Western blot. In the figure, C is the mature form of CFTR, glycosylated and expressed at the cell surface. B is the lower molecular weight, non glycosylated, form of the protein. The protein "tub" is tubulin and is used as a loading control to show there actually is protein in all of the samples.
a. Study Figure 1. Does the mutation V232D affect the expression levels of CFTR? Indicate which two lanes you compared to draw this conclusion.
The authors then treated the cells with two experimental drugs, Corr-4a and VRT-532, designed to improve the folding and stability of CFTR. DMSO is a solvent used to dissolve the drug compounds.
b. Re-examine Figure 1. Which drug is more effective at improving the stability of CFTR?
c. How does this mutation raise the possibility that the parents could have a child with cystic fibrosis?
2. Cystic fibrosis (CF) is a genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. CF is inheritance. It is caused by the presence of mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. A normal couple intends to have children but consult a genetic counselor because the man has a sister with CF and the woman has a brother with CF. There are no other known cases in their family. They want to know:
(1) What is the probability that their first child would be normal?
(2) What is the probability that their first two children would have CF?
(3) If they would like to have five children, what is the probability that at least two of them would be normal?
3. Cystic fibrosis (CF) is a genetic disease caused by a mutation in the CFTR gene. One of the distinguishing features is the thick mucus that lines both the airways and the intestinal tract of affected individuals. One of the mutations associated with CF is related to a chloride ion transporter. In healthy individuals, the chloride channels open periodically to allow the cell to maintain a normal balance of chloride ions between the inside and outside of the cell. In CF individuals, these chloride channels do not function, and chloride ions build up inside the cell.
a. Explain using the concept of water potential why the misfolding of the ion channel CFTR leads to thick mucus lining the tissues of the lungs and intestines.
b. Describe the mechanism of cell communication involved as seen in the diagram. A new drug to treat a particular type of CFTR is a modified protein. Describe two considerations for protein engineers to keep consistent to ensure proper functioning of the protein.
4. Sarah and Michael elected to have Sarah's DNA further analyzed. A week later they met again with the genetic counselor to discuss the test result. "So do I have a mutation in my CF gene?” asked Sarah. 'Yes,” the genetic counselor replied. “You have a rare allele called V232D. This mutation affects the folding of the CFTR protein. Because they don’t fold correctly proteins expressed from the V232D allele are not stable and usually do not make functional channels at the cell membrane.”
In their first experiment, the authors looked at expression of the CFTR protein expressed from the wild type (CFTR) or mutant (CFTR V232D) alleles in HEK-293 human kidney cells using a Western blot. In the figure, C is the mature form of CFTR, glycosylated and expressed at the cell surface. B is the lower molecular weight, non glycosylated, form of the protein. The protein "tub" is tubulin and is used as a loading control to show there actually is protein in all of the samples.
a. Study Figure 1. Does the mutation V232D affect the expression levels of CFTR? Indicate which two lanes you compared to draw this conclusion.
The authors then treated the cells with two experimental drugs, Corr-4a and VRT-532, designed to improve the folding and stability of CFTR. DMSO is a solvent used to dissolve the drug compounds.
b. Re-examine Figure 1. Which drug is more effective at improving the stability of CFTR?
c. How does this mutation raise the possibility that the parents could have a child with cystic fibrosis?
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