Ribonucleic acid (RNA) exists as a polymer constructed of four kinds of nucleotides. Ribonucleic acids are ordinarily involved in the conversion of genetic information from DNA into protein: information flows from the genetic material via RNA for the fabrication of an organism. Ribosomes are cytoplasmic particles structured of protein and ribosomal RNA (rRNA) and are the sites of protein synthesis. Messenger RNA (mRNA), transcribed from genomic DNA, translocates genetic information to the ribosomes. In addition, there are about 20 transfer RNAs (tRNA), which bind to specific amino acids and to particular regions of mRNA for the assembly of amino acids into proteins. The genetic material of some viruses is RNA.