Cell-to-cell variability in gene expression level (noise) has emerged as one of the fundamental concepts in genetics. Non-genetic, cell-to-cell variation in the abundance of a gene product can generate a diversity of behaviour in genetically identical population of cells. This phenomenon is pervasive and prevalent in development (e.g. stem cells) and disease (e.g. cancer). Genome-scale studies on gene expression noise have revealed that some genes are more random in their expression than others.
