Figure 3.—
Dynamics of an active trans (τ = 0) modifier allele M (black/dark lines) and the two chromosomes carrying it: the “active-hot” chromosome (HM, magenta/medium lines) and the “active-cold” chromosome (hM, blue/light lines) under a variety of selection regimes. Note that the scales of both the x- and the y-axes change from section to section. Exact (nonapproximated) differential equations were solved numerically, starting from fixation (thick dashed lines) or near-fixation (pH = 0.99, thin solid lines) of the H allele and near-fixation of the m allele (pHM = 10−3; pHm = 1 − 10−3). Other parameter values are μ = 10−6, ν = 10−7, βh = 10−8, hM = hm = 0, and 
; varying these parameters varies the rates of these processes but not the range of outcomes.