If I have a decrease or increase in expression in one gene, will the decrease/increase in expression in the downstream genes always be of a magnitude lower than the previous ones, or can they be higher?
I’m thinking in terms of signal propagation in a network. If I, for example, knockdown gene $X$ to 40% of its basal level, and it influences genes $Y$ and $Z$ in the following manner:
$$X → Y → Z,$$
Will I expect genes $Y$ and $Z$ to suffer lower decreases/increases than the previous gene, for example:
$$X: 40\% ~⇒~ Y: 60\% ~⇒~ Z: 80\%$$
Or could I have a scenario where a small change in one gene’s expression can lead to higher magnitude changes in downstream ones, for example:
$$X: 40\% ~⇒~ Y: 20\% ~⇒~ Z: 10\%$$
I suppose that in some networks the signal will always decrease in magnitude the farther it is from the source, but I’m wondering if, in a biological network, that will also happen and consistently in each step. I read papers with knockdowns all the time, but I never stopped to analyse if knockdowns always create lower magnitude changes in downstream genes or not. So I was wondering if this intuitive notion holds empirically or not.