0.3
0.7
0.49
0.42
0.09
42
%
90
0.3
0.7
0.49
0.42
0.09
42
%
90
The Hardy-Weinberg Equilibrium Calculator determines allele and genotype frequencies in a population that is not evolving. The Hardy-Weinberg principle states that allele and genotype frequencies remain constant from generation to generation in the absence of evolutionary influences such as selection, mutation, migration, and genetic drift.
Given the frequency of the homozygous recessive phenotype in a population, this tool calculates all allele and genotype frequencies under Hardy-Weinberg assumptions.
The Hardy-Weinberg equations are:
p + q = 1 (allele frequencies)
p² + 2pq + q² = 1 (genotype frequencies)
Where p = frequency of the dominant allele (A), q = frequency of the recessive allele (a), p² = frequency of AA genotype, 2pq = frequency of Aa genotype, and q² = frequency of aa genotype.
Given q² (observable as the recessive phenotype frequency): q = √q² and p = 1 − q.
Inputs
Results
If 1 in 2,500 people have cystic fibrosis (q²=0.0004), then q=0.02, and the carrier frequency (2pq) is approximately 3.92% or about 1 in 25 people.
Inputs
Results
If 9% of a population cannot taste PTC (recessive phenotype), then the recessive allele frequency is 0.3. About 42% are heterozygous carriers who can taste PTC.
Five conditions must be met: (1) no natural selection, (2) no mutation, (3) no migration (gene flow), (4) infinitely large population (no genetic drift), and (5) random mating. In reality, no natural population perfectly meets all conditions, but the model provides a useful null hypothesis for detecting evolutionary forces.
Compare observed genotype frequencies to expected Hardy-Weinberg frequencies using a chi-square goodness-of-fit test. If the observed and expected values do not differ significantly (p > 0.05), the population is consistent with Hardy-Weinberg equilibrium. Significant deviations suggest evolutionary forces are acting.
The Hardy-Weinberg principle serves as a baseline for studying evolution. By comparing real populations to Hardy-Weinberg expectations, geneticists can identify which evolutionary forces are at work. It is also practically important in medical genetics for estimating carrier frequencies of recessive diseases in populations.
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