RNA

Ribonucleic acid (RNA) can serve as genetic material in viruses, such as in the Human Immunodeficiency Virus - HIV, but in living cells it serves for protein synthesis and gene expression regulation. Ribonucleic acid (RNA) is biosynthesized from the genetic material of the cell, deoxyribonucleic acid (DNA), in a process called transcription. Both RNA and DNA are polymers, or long chains, of nucleic acids. There are four different nucleic acids in RNA and DNA molecules, but they differ by the presence of only one nucleic acid, as discussed below. There are several types of RNA molecules synthesized from DNA which have various functions in protein synthesis: carrying the codes needed, serving as the production sites and transferring of amino acids to growing protein chains. http://www.nature.com/nature/journal/v442/n7099/full/nature04917.html http://www.elmhurst.edu/~chm/vchembook/583rnatypes.html

In RNA the nucleotide uracil (U) is substituted for thymine (T), otherwise the complement of nucleotides are the same as DNA. The DNA nucleotides are adenine (A), guanosine (G), cytosine (C) and thymine. Instead of an A-T pairing for DNA to DNA synthesis, for RNA synthesis, there would be an A-U pairing and the G-C pairing remains the same. There are three types of RNA based on their function for protein synthesis in the cell: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA) which all have different essential functions in cell metabolism as discussed in the Fast Facts section. http://www.elmhurst.edu/~chm/vchembook/583rnatypes.html