TH Nelson

Micro ribonucleic acid are small, single-stranded, non-coding RNA molecules containing 21–23 nucleotides. Found in plants, animals, and even some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. miRNAs base-pair to complementary sequences in messenger RNA (mRNA) molecules, then silence said mRNA molecules by one or more of the following processes:Cleaving the mRNA strand into two pieces.
Destabilizing the mRNA by shortening its poly(A) tail.
Reducing translation of the mRNA into proteins.