The disease cystic fibrosis (CF) is the most common genetic
disorder in the US. People affected by this disease are lacking a
cell membrane transport protein that controls the flow of chloride
ions across the cellular membrane. This flow of chloride ions (Cl-
), in turn, affects water moving out of cells. When enough water
does not move out of cells, mucus in the lungs is not diluted and
it builds up in the ducts and airways, providing a good medium for
bacterial growth. Other organs with ducts are similarly affected
and clogged. Scientists have discovered that the mutated gene
causing this disease is missing an entire codon, so people with CF
have an abnormal Cl- transport protein, or are missing it
altogether.

a. Explain in step-by-step detail how the normal transport
protein would be made going from gene to functional protein. In
your answer, include the process(es) or “pathway(s)” that the
information “follows” as 5 it “flows” from gene to protein to
functional protein, as well as where in the cell each step
happens.

b. Explain all of the ramifications of deleting a single codon
in the gene that produces this Cl- transport protein. In other
words, based on your knowledge of protein synthesis, and on protein
processing in cellular organelles, explain why even though this
impacted protein may be manufactured in people with CF, it cannot
perform its designated function, and/or may not even be inserted
into the cellular membrane. Explain the reasons why/how this single
mutation can mess everything up.