. In Europe, the frequency of the CF− allele causing therecessive autosomal disease cystic fibrosis is about0.04. Cystic fibrosis causes death before reproductionin virtually all cases.a. Determine values of relative fitness (W) for the unaffected, carrier, and affected genotypes. Assumethat no selective advantage is associated with heterozygosity for the disease allele.b. Given your answer to part (a), determine the average (mean) fitness at birth of the population as awhole with respect to the cystic fibrosis trait (W)and the expected change in allele frequency overone generation (Δq) when measured at the birth ofthe next generation.c. Suppose the European population is at equilibriumfor the frequency of the CF− allele because someheterozygote advantage exists. Recalculate the relative fitness values for the three genotypes underthis assumption. d. The CFTR protein encoded by the CF gene is achloride ion channel. People suffering from cholerahave diarrhea that pumps water and chloride ionsout of the small intestine. Use these facts to explainwhy a heterozygote advantage might in fact existfor the CF gene.
. In Europe, the frequency of the CF− allele causing the
recessive autosomal disease cystic fibrosis is about
0.04. Cystic fibrosis causes death before reproduction
in virtually all cases.
a. Determine values of relative fitness (W) for the unaffected, carrier, and affected genotypes. Assume
that no selective advantage is associated with heterozygosity for the disease allele.
b. Given your answer to part (a), determine the average (mean) fitness at birth of the population as a
whole with respect to the cystic fibrosis trait (W)
and the expected change in allele frequency over
one generation (Δq) when measured at the birth of
the next generation.
c. Suppose the European population is at equilibrium
for the frequency of the CF− allele because some
heterozygote advantage exists. Recalculate the relative fitness values for the three genotypes under
this assumption. d. The CFTR protein encoded by the CF gene is a
chloride ion channel. People suffering from cholera
have diarrhea that pumps water and chloride ions
out of the small intestine. Use these facts to explain
why a heterozygote advantage might in fact exist
for the CF gene.
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