To calculate the frequency of carriers for cystic fibrosis (CF) in the Caucasian population of the
United States, we can follow these steps:
Calculate the frequency of the recessive allele in the population:
Let's assume "p" represents the frequency of the dominant allele and "q" represents the frequency
of the recessive allele. Since CF is a recessive condition, the frequency of the recessive allele can
be calculated using the square root of the CF prevalence (1 in 2,500 babies):
q = √(1 / 2500)
Calculate the square root: q ≈ 0.0142
Calculate the frequency of the dominant allele in the population:
Since there are only two alleles (dominant and recessive) for the CF gene, the frequency of the
dominant allele can be found by subtracting the recessive allele frequency from 1:
p=1-q
p ≈ 1 - 0.0142
p ≈ 0.9858
Calculate the percentage of heterozygous individuals (carriers) in the population:
The frequency of heterozygotes can be calculated using the 2pq formula, where "p" and "q" are
the allele frequencies calculated in the previous steps:
2pq ≈ 2 * 0.9858 * 0.0142
2pq ≈ 0.0279
To convert this to a percentage, multiply by 100:
Percentage of carriers ≈ 0.0279 * 100
Percentage of carriers ≈ 2.79%
Calculate the frequency of carriers:
The frequency of carriers is the same as the percentage of carriers, expressed as a decimal:
Frequency of carriers ≈ 2.79% (or 0.0279)
Therefore, the frequency of carriers for cystic fibrosis in the Caucasian population of the United
States, assuming random mating, is approximately 2.79% or 0.0279.