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Cystic Fibrosis


Cystic fibrosis (CF) is a condition affecting secretory glands, such mucus and sweat glands. People with CF produce a thick sticky mucus which leads to a wide range of problems, including digestive issues and greater susceptibility to lung infections.

Males with CF are typically infertile. People with CF historically had a short lifespan, although people are now living longer as treatments improve. CF is caused by a mutation to the CFTR gene, which codes for a protein that transports chloride ions across the cell membrane.

In the U.S., the condition occurs in up to one of every 2,500 newborns of European decent. Only one in 17,000 African Americans and one in 31,000 Asian Americans are affected.

Which of the following hypotheses could explain the increased prevalence of CF in European populations?


Carriers of a mutated CFTR gene are resistant to a disease that historically affected European populations.


Individuals with CF have a higher fitness at higher latitudes​.


The CFTR gene is linked to the IRF5 gene, which is tied to autoimmune problems.


The CFTR gene originated in Europe.