Study sheet for Cystic Fibrosis:
The “C” (normal allele) for the CFTR gene is transcribed and translation happens to give
a normal CFTR protein.
1. Where does the normal CFTR protein go within the cell?
2. What is the protein’s normal job?
3. The “C” (normal allele) for the CFTR gene is “haplo-sufficient”. What does that
mean?
A “loss of function” mutation in the CFTR gene is any mutation results in either no
protein being produced from the allele or a non-functional protein being produced by the
allele. F508del and G551D are both loss-of-function mutations of the CFTR gene.
4. What is the effect on a person’s phenotype if they carry only loss-of-function
alleles for this important gene?
The G551D allele for the CFTR gene has a slightly different DNA sequence that
produces a protein with one amino acid different from the normal CFTR protein.
5. What effect does the altered amino acid have on the protein?
6. Where is the G551D-CFTR protein found in the cell?
7. How does the G551D protein act in the cell? Why does this cause disease?
The F508del mutation for the CFTR gene is missing 3 bp of the gene, resulting in a
protein with one less amino acid than the normal protein.
8. What effect does having one less amino acid have on the protein?
9. What happens to the F508del-CFTR protein in the cell? Why does this cause
disease?