Micro RNAs (miRNAs) are created from microgenes and are a molecule approximately 22 base pairs long. They are thought to coordinate the expression of protein-coding genes in eukaryotes. More than 1000 have been discovered and they appear to compromise a secondary level of control that probably coordinates genome function in humans and other complex organisms (Elliot and Elliot). These miRNAs are also known to help initiate mRNA degradation and prevent the translation of mRNA into proteins through a process known as RNA interference. (Pierce, Benjamin A). There is a miRNA-induced silencing complex (miRISC) that links to mature miRNAs. This forms a complex that blocks translation through binding to the mRNA. MiRNAs (Phillips, Theresa) are capable of targeting up to several hundred genes through binding to different regions and imperfect base pairing. (Larson, Richard A) miRNAs are a class of non-coding RNAs that regulate gene expression by binding to complementary regions; this is commonly done with the 3'UTR of the target mRNA resulting in mRNA degradation and translational repression. (Goodal). Bound to an argonaute protein, all miRNAs require it for miRNA function (Nilsen, Timothy W. Gene regulation is the process of turning genes in our cells on and off when they are required. This is necessary because every cell in our body has a complete protein set of the genome and the difference between cells is which genes are expressed and not expressed within them. Differentiation between cells is due to different regulatory elements (Yoon, Wan Hee). occurs at the level of transcription in cells. The promoters and repressors of operons are all strong...... half of the article ......illiam H Elliot and Daphne C ElliotGenetics: A Conceptual Approach, Fourth Edition, 2012Small Non - RNA coding and gene expression By: Theresa Phillips, Ph.D. (Write Science Right) © 2008 Nature Education) the role of microRNAs in development, department of biological chemistry of the John Hopkins University biowave school of medicine vol 11 no 11 2009 Wan Hee Yoon• MicroRNAs and copy number changes: new levels of gene regulation in acute myeloid leukemia Richard A. Larson, MD 2010 March 19• The role of microRNAs in tumorigenesis and angiogenesis Weining Yang1, Daniel Y Lee 2, Yaacov Ben-David1 Accepted June 11, 2011.FOXP3 regulated microRNA: a novel component of FOXP3 tumor suppressor function in breast epithelial cells: Goodal, Brown, Brown, Cowin, and venterMicroRNA: SMALL RNAs WITH A BIG ROLE IN GENE REGULATION In He and Gregory J. Hannon