What is RNA?
[[File:Pre-mRNA-1ysv-tubes.png|thumb|A hairpin loop from a pre-mRNA. Highlighted are the [[nucleobase]]s (green) and the ribose-phosphate backbone (blue). This is a single strand of RNA that folds back upon itself. ]] '''RNA''' is an [[acronym]] for '''ribonucleic acid''', a [[nucleic acid]]. Many different kinds are now known.<ref>Only the most important are described here. A complete list is available at [[:en:List of RNAs]].</ref> RNA is physically different from [[DNA]]. DNA has two [[Strand|strands]] that twist around each other, but RNA only has one strand. RNA also has different [[Nucleotide|bases]] than DNA. These bases are [[adenine]], [[guanine]], [[cytosine]], and [[uracil]]. Adenine bonds with uracil. Guanine bonds with cytosine. In this way, we say that adenine is complementary to uracil and that guanine is complementary to cytosine. Adenine, guanine and cytosine are also in DNA. In RNA, [[uracil]] replaces [[thymine]] as a complement to adenine. '''RNA''' also has [[ribose]]. This is different from the [[deoxyribose]] in DNA. These differences result in RNA being more chemically reactive than DNA. This makes it the more suitable [[molecule]] to take part in cell reactions. RNA is the carrier of [[Genetics|genetic]] information in certain [[virus]]es, especially [[retrovirus]]es like [[HIV]]. This is the only exception to the general rule that DNA is the [[Heredity|hereditary]] substance. == Protein synthesis RNAs == === Messenger RNA === [[File:MRNA structure.svg|thumb|650px|center|The structure of a mature eukaryotic mRNA. A fully processed mRNA includes a [[5' cap]], [[5' UTR]], [[coding region]], [[3' UTR]], and poly(A) tail. UTR = untranslated region]] The main function of RNA is to carry information of [[amino acid]] sequences from the [[Gene|genes]] to [[ribosomes]] in the [[cytoplasm]]. Ribosomes are where proteins are assembled. This is done by '''[[messenger RNA]]''' (mRNA). A strand of DNA is the blueprint for the mRNA which is [[Transcription (genetics)|transcribed]] from that DNA