1. Cystic fibrosis is a chronic lung and digestive disease caused by a mutation in the CFTR gene on chromosome 7. In the United States approximately 39 in 10,000 individuals are affected with the recessive condition cystic fibrosis, 323 in 10,000 individuals are unaffected carriers, and 9,638 out of 10,000 individuals are unaffected non-carriers. Although there are over 1,000 known mutations in the CFTR gene that can lead to cystic fibrosis, we can determine the overall frequency of recessive alleles in the U.S. population.
a)Calculate the observed frequency of CFTR alleles :
CFTR dominant (unaffected) alleles =
CFTR recessive (cystic fibrosis) alleles =
b)The expected frequency of CFTR genotypes :
Homozygous dominant (unaffected) =
Heterozygous (unaffected carriers) =
Homozygous recessive (affected) =
c)Next, use the following chi-squared analysis table to determine if the U.S. population is in Hardy-Weinberg equilibrium for the recessive condition, cystic fibrosis.
Degrees of Freedom = 1
Critical Value = 3.84