micro RNA (miRNA)

A microRNA (abbreviated miRNA) is a small single-stranded non-coding RNA molecule (containing about 22 nucleotides) found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression. miRNAs function via base-pairing with complementary sequences within mRNA molecules. As a result, these mRNA molecules are silenced, by one or more of the following processes:

(1) cleavage of the mRNA strand into two pieces,
(2) destabilization of the mRNA through shortening of its poly(A) tail,
(3) less efficient translation of the mRNA into proteins by ribosomes