Editing Cloning vector (section)

{{Short description|Small piece of maintainable DNA}}
[[File:PBR322 color.svg|thumb|Schematic representation of the [[pBR322]] plasmid, one of the first plasmids widely used as a cloning vector.]]

A '''cloning vector''' is a small piece of [[DNA]] that can be stably maintained in an organism, and into which a foreign DNA fragment can be inserted for [[molecular cloning|cloning]] purposes.<ref>{{cite web |url=http://www.theodora.com/genetics/#cloningvector |title=Definition of cloning vector |work=Genome Dictionary |access-date=2012-10-18}}</ref> The cloning vector may be DNA taken from a [[virus]], the [[Cell (biology)|cell]] of a higher organism, or it may be the [[plasmid]] of a bacterium. The [[Vector (molecular biology)|vector]] contains features that allow for the convenient insertion of a DNA fragment into the vector or its removal from the vector, for example through the presence of [[restriction site]]s. The vector and the foreign DNA may be treated with a [[restriction enzyme]] that cuts the DNA, and DNA fragments thus generated contain either blunt ends or overhangs known as sticky ends, and vector DNA and foreign DNA with compatible ends can then be joined by [[Ligation (molecular biology)|molecular ligation]].  After a DNA fragment has been cloned into a cloning vector, it may be further [[subcloned]] into another vector designed for more specific use.

There are many types of cloning vectors, but the most commonly used ones are genetically engineered [[plasmid]]s.  Cloning is generally first performed using ''[[Escherichia coli]]'',  and cloning vectors in ''E. coli'' include plasmids, [[bacteriophage]]s (such as [[Lambda phage|phage λ]]), [[cosmids]], and [[bacterial artificial chromosome]]s (BACs).  Some DNA, however, cannot be stably maintained in ''E. coli'', for example very large DNA fragments, and other organisms such as yeast may be used.  Cloning vectors in yeast include [[yeast artificial chromosome]]s (YACs).