Before revision: Based on data on gene expression profiles from microarrays for E. Coli and tumor tissues, I show that the evolution for thousands of generations leads to a set of strongly over- and under-expressed genes, as compared to the initial expression profile.
After revision: In many situations, the gene expression signature is a unique marker of the biological state. We study the modification of the gene expression distribution function when the biological state of a system experiences a change. This change may be the result of a selective pressure, as in the Long Term Evolution Experiment with E. Coli and tumor tissues, I show that the evolution for thousands of generations leads to a set of strongly over- and under-expressed genes, as compared to the initial expression profile.