Figure 1.

The potential role of RNAs in the regulation of gene expression. For the purposes of this article a gene is loosely defined as a transcription unit that may produce either protein-coding sequence (mRNA) or noncoding RNA (ncRNA), or in some cases both. The flow of genetic information from gene to a functional protein or RNA is indicated by the black arrows. Noncoding RNAs can act to regulate the expression of genes at multiple points (gray arrows). Black text refers to physical entities such as DNA and RNA, while red text refers to activities. Figure courtesy of and adapted from J. Mattick.