Under-Dominance Constrains the Evolution of Negative Autoregulation in Diploids
Figure 5
Intrinsic noise in gene expression.
The figure shows quantitative results for the intrinsic noise of autoregulating genes, as measured by the ratio of the variance to mean expression in protein concentration at equilibrium. (a) Percentage change in the noise of a heterozygote compared to the resident homozygote. These are shown for different Hill coefficients, (black),
(red) and
(blue). Mutations become deleterious in the heterozygote when
. (b) Percentage change in the noise of a mutant homozygote compared to the resident homozygote. Mutations become deleterious in the mutant homozygote when
is about
. The graphs show the results of stochastic simulations (see Materials and Methods) for parameter values typical for transcription factors [3],
,
,
,
and
. The resident homozygote has binding strength
(as indicated by the x-axis), mutations are of size
.