W₂

                   or             1    =    1       1-s

q     = [pq] [(q)(W₂ - W₁) + (p)(W₁ - W₀)] / []                                     [GSM]

          = [pq] [(q)(1 - s) - 1)) + (p)(1 - 1)] / [p²(1) + 2pq(1) + q²(1 - s)]      [Fitness phenotypes W₀ = W₁ of AA & AB cancel; expand ]

          = [pq] [-sq] / [p² + 2pq + q² - sq²]                                                  [Sort out numerator; extract p² + 2pq + q² in denominator]

q    = -spq² / (1 - sq²)