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Chapter Week 2

CAS BI 203 Chapter Notes - Chapter Week 2: Ivacaftor, Physical Therapy, Lumacaftor

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CAS BI 203
Francis Monette
Week 2

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1. What do scientists currently believe is the cause of CF? In other words, how is
the faulty gene inherited and what direct effect does that have on the affected cells?
Cystic Fibrosis (CF) is a genetic disorder that primarily affects the respiratory and
digestive system. It usually affects them in the following ways; the protein produced by
this gene normally helps salt move in and out of cells, however, if not functioning
correctly it blocks the movement causing the production of abnormally thick, sticky
mucus to build up outside the cell. This makes it difficult for the lungs to clear,
increasing the risk of infection. CF is a recessive disorder, meaning both parents must
pass the defective gene on chromosome 7 (CFTR-cystic fibrosis trans-membrane
conductance regulator) on to their child.
2. Draw a flow chart/concept map that illustrates the mechanism whereby the faulty
CF gene causes the production of thick mucus with less water in it than normal.
Mutation in the CFTR gene
Production of defective CFTR protein
Defective CFTR protein in the cell membrane (or no protein at all) that causes impaired
ion transport across the cells membrane
Cells secrete less chloride
Leads to more absorption of sodium and water into the cells
Decreased hydration of mucus present outside the cells as more water is absorbed into
the cell
Thick, viscous mucus
3. What specific part of the cell/structure allows the mucus secretions to be thick
and viscous rather than fluid (i.e., is it a membrane channel, organelle or something
else)? Please be specific and describe the step-by-step mechanism whereby this
altered structure/part of the cell causes the secretions to contain less water.
4. Why does Alvin have salt crystals forming on his skin? Explain the mechanism
for this.
The salt crystals on Alvin’s skin is due to unabsorbed salt and excessive sweating.
Sweat glands cool the body by releasing perspiration (sweat) from the lower layers of
the skin onto the surface. Sodium and chloride (salt) help carry water to the skin's
surface and are then reabsorbed into the body. As the water evaporates, heat is carried
away, and the body cools. In Alvin’s case, the salt travels to the skin's surface with the
water and is not reabsorbed leaving his skin abnormally salty.
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