A category of nucleic acids which along with DNA forms the genetic material of a cell. While DNA stores the genetic information in the nucleus of every cell, RNA is a “carrier” of this information from DNA to other parts of the cell where the message is converted to protein. Structurally, RNA is a single-stranded structure. The component sugar that forms the backbone of RNA is ribose (as opposed to deoxyribose in DNA) and the four bases in RNA are Uracil, Guanine, Adenine and Cytosine (DNA contains Thymidine instead of Uracil). There are three types of RNA, all of which play an intermediary role in converting DNA information into protein: messenger RNA (mRNA) is a copy of the DNA in the nucleus and carries it to the cytoplasm where the cellular machinery for decoding that information lies; transfer RNA (tRNA) allows the code to be read three bases (one codon) at a time and transfers the information from RNA to protein (each tRNA carries one particular amino acid); and ribosomal RNA (rRNA) has a structural role forming part of the ribosome--the machinery that converts RNA into protein.