- Put your observed gamete frequencies or click the initiate Mendel
button. If the mothers gamete frequencies sum to zero, the frequencies
for the fathers is also applied for the mothers.
- Click on Next generation button calculate the gamete and genotype frequencies in next generation.
In all cells with initial values you can put data and to get the results press the Next generation button. Table values are rounded to the desired number of decimals.
Gamete Observed frequency Expected frequency Deviation -------------------------------------------------------------- AB r p(A)*p(B) D Ab s p(A)*q(b) -D aB t q(a)*p(B) -D ab u q(a)*q(b) D
The disequilibrium gets the symbol D can be calculated from the table above, and can also be calculated as the half of the difference in the frequency of double heterozygotes in linkage- and repulsion phase:
D = r*u - t*s (= [f(AB/ab) - f(Ab/aB)]/2) from the table aboveThe maximum disequilibrium occurs, when all double heterozygotes are in linkage phase f(AB/ab) or in repulsion phase f(Ab/aB). See the Figure below.
Are the recombination frequency c would D be reduced to D*(1-c) per generation, and for the n'th generation Dn = D0*(1-c)n.
If you apply the initial values r=0.1, s=0.2, t=0.3, u=0.4 and press the Next generation button, you will see calculated all the genotype frequencies and D=0.0199 rounded 0.02. If you continue using the Next generation button more times with c=0.5 you will see that D= approach 0 which means observed and expected gamete frequencies are equal i.e. r=0,12.
Gamete Observed frequency AB 0.21 Ab 0.49 aB 0.19 ab 0.11
What would be the frequencies of the two types of double heterozygotes
in next generation?
How many generations will it take to reach equilibrium within 0.02 units ? Repeat the calculations for c=0.05.
In a F3 after a cross between two pure lines aabb X AABB. What would
be the gamete frequencies if c=.5 , .4 and .1 ?
Hints: Use the initiate mendel button and use the next generation button more times.