These questions will focus on the population genetics of cystic fibrosis, an aut

Question

These questions will focus on the population genetics of cystic fibrosis, an autosomal recessive Mendelian condition caused by variants in the CFTR gene. The CFTR gene encodes a protein channel that allows chloride ions to pass in and out of the cell and is important for maintaining salt and water equilibria in multiple organs systems. Cystic fibrosis is characterized by lung problems, which can often lead to complications and early mortality. There are multiple variants in the CFTR gene that can cause CF; an individual who inherits two copies of the CFTR gene with any combination of these variants will develop the disease.

Cystic fibrosis is most common in individuals of Northern European descent, affecting 1 in 3200 newborns. Assuming that these alleles are at Hardy-Weinberg equilibrium, what is the frequency of the disease-causing CFTRalleles in this population?

0.03% incorrect

0.06%

1.8%

3.5%

Approximately what percent of individuals of Northern European descent are carriers of cystic fibrosis?

0.03%

0.06% incorrect

1.8%

3.5%

Explanation / Answer

H-W equilibrium:

p+q = 1

p2+2pq+q2 = 1

q2 = 1/3200 = 0.0003125

Frequency of the disease-causing CFTRalleles in this population, q = 0.017677

Frequency of WT alelle, p = 1-0.017677 = 0.982323

Frequency of carriers, 2pq = 2 * 0.982323 * 0.017677 = 0.03472

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