ABSTRACT
Most genes studied in earlier chapters encoded proteins. In this chapter, we turn to a group of genes that are transcribed but not translated. MicroRNAs (miRNA, pronounced either microRNA or em-eye-RNA) are approximately 22-nucleotide sequences that repress the translation of protein-coding mRNAs. MicroRNA genes are far from being minor curiosities. In fact, the study of miRNAs and their effect on biology and human disease has been one of the most active areas of research in recent years, generating over 10,000 publications since the discovery of miRNAs in 1993. Testament to their importance, miRNAs are unchanged in sequence for at least 450 million years of evolution.
