Equilibrium Hardy-Weinberg
Hardy-Weinberg equilibrium law states that allele and genotype frequencies in a population will remain constant from one generation to next generation in the absence of disturbing factors. In this calculator, Hardy-Weinberg equilibrium can be used to calculate the expected common homozygotes, expected heterozygotes, expected rare homozygotes and the frequency range of the 2 (p and q) alleles from the observed genotypes.
Calculator of Hardy-Weinberg equilibrium
Formula of Hardy-Weinberg equilibrium
pfreq = (CH + (0.5 * H)) / (CH + H + RH)
qfreq = (RH + (0.5 * H)) / (CH + H + RH)
ECH = pfreq * pfreq * (CH + H + RH)
EH = 2 * pfreq * qfreq * (CH + H + RH)
ERH = qfreq * qfreq * (CH + H + RH)
chi1 = ((CH - ECH) * (CH - ECH)) / ECH
chi2 = ((H - EH) * (H - EH)) / EH
chi3 = ((RH - ERH) * (RH - ERH)) / ERH
chi2 = chi1 + chi2 + chi3
- CH = Common Homozygotes
- H = Heterozygotes
- RH = Rare Homozygotes
- ECH = Expected Common Homozygotes
- EH = Expected Heterozygotes
- ERH = Expected Rare Homozygotes
- pfreq = p Allele Frequency
- pfreq = q Allele Frequency
It is also known as Hardy-Weinberg principle, model, theorem.
Example of Hardy-Weinberg equilibrium
If the observed common homozygotes is 21, heterozygotes is 10 and rare homozygotes is 2, then
Step 1 : p Allele Frequency
pfreq =
= (21 + (0.5 * 10)) / (21 +10 + 2)
= (21 + 5) / 33
= 0.7879
Step 2 : q Allele Frequency
qfreq =
= (2 + (0.5 * 10)) / (21 + 10 + 2)
= 7 / 33
= 0.2121
Step 3 : Expected CH
Expected CH =
= 0.78 * 0.2121 * (21 + 10 + 2)
= 20.48
Step 4 : Expected H
Expected H =
= 2 * 0.78 * 0.2121 * (33)
= 11.03
Step 5 : Expected RH
Expected RH = 1.4848
Step 6 : Chi Square
chi1 = ((CH - ECH) * (CH - ECH)) / ECH
chi1 = ((21 - 20.4848) * (21- 20.4848)) / 20.4848
chi1=0.0129
chi2 = ((H - EH) * (H - EH)) / EH
chi2 = ((10 - 11.0303) * (10 - 11.0303)) / 11.0303
chi2 = 0.0962
chi3 = ((RH - ERH) * (RH - ERH)) / ERH
chi3 = ((2 - 1.4848) * (2 - 1.4848)) / 1.4848
chi3 = 0.1787
chi2 = chi1 + chi2 + chi3
chi2 = 0.0129+0.0962+0.1787
chi2 =0.2879