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The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated.〔(Technical Glossary ) Edward K. Wagner, Martinez Hewlett, David Bloom and David Camerini ''Basic Virology'' Third Edition, Blackwell publishing, 2007 ISBN 1-4051-4715-6〕 This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses. DNA replication may proceed from this point bidirectionally or unidirectionally. The specific structure of the origin of replication varies somewhat from species to species, but all share some common characteristics such as high AT content (repeats of adenine and thymine are easier to separate because their base stacking interactions are not as strong as those of guanine and cytosine〔http://nar.oxfordjournals.org/content/34/2/564.full〕). The origin of replication binds the pre-replication complex, a protein complex that recognizes, unwinds, and begins to copy DNA. == Types == The two types of replication origin are: * Narrow or broad host range * High- or low-copy number There are also significant differences between prokaryotic and eukaryotic origins of replication: * Most bacteria have a single circular molecule of DNA, and typically only a single origin of replication per circular chromosome. * Most archaea have a single circular molecule of DNA, and several origins of replication along this circular chromosome. * Eukaryotes often have multiple origins of replication on each linear chromosome that initiate at different times (replication timing), with up to 100,000 present in a single human cell. Having many origins of replication helps to speed the duplication of their (usually) much larger store of genetic material. The segment of DNA that is copied starting from each unique replication origin is called a replicon. Origins of replication are typically assigned names containing "''ori''". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Origin of replication」の詳細全文を読む スポンサード リンク
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