Experimental populations of Drosophila pseudoobscura were established and period

Question

Experimental populations of Drosophila pseudoobscura were established and periodically treated with weak doses of the insecticide DTT. One population was initially polymorphic for five different inversions in the third chromosome, in approximately equal frequencies. After 13 generations, three of the inversions had disappeared from the population. The two that remained were Standard (ST) and Arrowhead (AR). Changes in frequency of each inversion were monitored, and from the values for the first nine generations the relative fitness of ST/ST, ST/AR, and AR/AR genotypes were estimated as 0.47, 1.0, and 0.62, respectively. Because the inversions yield almost no recombinant gametes, each type (ST or AR) can be considered as an

Explanation / Answer

genotype ST or allele p (frequency of p2) = 0.47

Then p = 0.69, Then q = 1 - p = 1 - 0.69 = 0.31

Equilibrium frequency of ST (p`) is = (p2 WRR + pq WRr)/normalizing factor (W^)

p` = (0.47) (0.47) + (0.69) (0.31) (1)/0.83 = 0.22+0.21/0.83= 0.5

average fitness(W^) = p2 WRR + 2 pq WRr + q Wrr

         = (0.47)2 + 2 (0.69 x 0.31 ) 1 +( 0.31) (0.62) = 0.22+0.42+0.19 = 0.83

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