  Gene expression is inherently noisy as many steps in the read-out of the
genetic information are stochastic. To disentangle the effect of different
sources of stochasticity in such systems, we consider various models that
describe some processes as stochastic and others as deterministic. We review
earlier results for unregulated (constitutive) gene expression and present new
results for a gene controlled by negative autoregulation with cell growth
modeled by linear volume growth.
