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Figure 2.20 The decay of gametic disequilibrium (D) over time when both strong natural selection and recombination are acting. Initially, there are only coupling (Pn = P22 = V2) and no repulsion gametes (P12 = P21 = 0). The relative fitness values of the AAbb and aaBB genotypes are 1 while all other genotypes have a fitness of 1/2. Unlike in Fig. 2.19, gametic disequilibrium does not decay to zero over time due to the action of natural selection.

fitness genotypes, which will also reduce the number of gametes these genotypes contribute to forming the next generation. At the same time that natural selection is acting, recombination is also working to randomize the associations of alleles at the two loci. Figure 2.20 shows an example of this type of natural selection acting in concert with recombination to maintain gametic disequilibrium.

The action of natural selection acting on differences in gamete fitness can produce steady states other than D = 0, expected eventually under even free

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