|In Depth||Is Phenotypic Noise a Product of Natural Selection?|
|Stochasticity has also been theorized to have implications in disease and development. While significant results are still pending, haploinsufficiency diseases are thought to arise in part from stochasticity in gene expression. This theory is based on the idea that a single functional allele cannot produce the amount of protein needed to keep the body's respective protein concentration continually above a low threshold state due to the pulsatile nature of mRNA production. Stochasticity may also play a role in stem cell differentiation. Stochasticity initially establishes heterogenity within an initially homologous population that allows for the selection of cell-type-specific gene expression and eventually differentiation (Eisen, 2004).
In the study of stochasticity and gene expression the obvious question seems to be: Why are certain processes so noisy? From an evolutionary standpoint, it seems counterintuitive that natural selection would allow complex systems to exhibit protein expression behavior that is variable and unpredictable.