p' = p[pW_AA+ qW_Aa] / [p²W_AA+ 2pqW_Aa +  q²W_aa]

To calculate the trajectories in the following graphs, values of the W's and an initial gene frequency, p, were inserted into this equation, and the equation was then iterated over a number of generations.

    These graphs are taken from J. Roughgarden.  1979.  Theory of Population Genetics and Evolutionary Ecology: An Introduction.  MacMillan, New York, NY.

I. Selection favoring a recessive allele, a, and against a dominant allele, A.

II.  Selection favoring a dominant allele, a, and against a recessive allele, A.

III.  Selection against allele A, with heterozygote having intermediate fitness.  In this graph, W_AA= 1,
        W_Aa = 1- s, and W_aa = 1- 2s. 

IV.  Selection under heterozygote superiority.   In the top graph, W_AA= 1-s, W_Aa = 1, and W_aa = 1- s.
       In the bottom graph, W_AA= 1-s, W_Aa = 1, and W_aa = 1- 2s.
 
 

V.  Selection under heterozygote inferiority.  In this graph, W_AA= 1 + s, W_Aa = 1, and W_aa = 1+ s.
 
 
 
 

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