Many studies have been conducted to assess the prevalence of cystic fibrosis in
ID: 58028 • Letter: M
Question
Many studies have been conducted to assess the prevalence of cystic fibrosis in different populations. Below is data from four such studies.
Phenotypes
Population Non cystic fibrosis Cystic fibrosis Total # individuals
Non-Hispanic Caucasians 17,433 7 17,440
Hispanic Caucasians 13,534 1 13,535
African-Americans 15,124 1 15,125
Estimate the frequency (q) of the cystic fibrosis allele in each population.
Estimate the expected genotype frequencies in each population.
Why do you think the prevalence of cystic fibrosis varies between these populations?
Explanation / Answer
1) Estimated frequency of cystic fibrosis allele in Non-Hispanic Caucasians = 7/17440 = 1-0.999 = 0.001
Estimated frequency of non cystic fibrosis allele in Non-Hispanic Caucasians = 17433/17440 = 0.999
Estimated frequency of non- cystic fibrosis allele in Hispanic Caucasians = 13534/13535 = 0.999
Estimated frequency of cystic fibrosis allele in Hispanic Caucasians = 1/13535 = 1 - 0.999 = 0.001
Estimated frequency of non-cystic fibrosis allele in African-Americans = 15124/15125 = 0.999
Estimated frequency of cystic fibrosis allele in African-Americans = 1/15125 = 1- 0.999 = 0.001
2)
Estimated genotype frequencies for non-Hispanic Caucasians (homozygous dominant) = (0.999) (0.999) = 0.998
Estimated genotype frequencies for non-Hispanic Caucasians (heterozyous) = (0.999) (0.001) = 0.0009
Estimated genotype frequencies for non-Hispanic Caucasians (homozygous recessive) = (0.001) (0.001) = 0.000001
In Hispanic Caucasians and African-Americans, the genotype frequencies are same as in case of non-Hispanic Caucasians.
3)
The recessive gene encoding cystic fibrosis is exhibited in certain race of population such as non-Hispanic Caucasians, Hispanic - Caucasians and African - Americans.
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