coli vectors, which contain elements necessary for their maintenance in E. The manipulation of DNA is normally conducted on E. Transcription vectors are used to amplify their insert. Simpler vectors called transcription vectors are only capable of being transcribed but not translated: they can be replicated in a target cell but not expressed, unlike expression vectors. Vectors designed specifically for the expression of the transgene in the target cell are called expression vectors, and generally have a promoter sequence that drives expression of the transgene.

All vectors may be used for cloning and are therefore cloning vectors, but there are also vectors designed specially for cloning, while others may be designed specifically for other purposes, such as transcription and protein expression. The purpose of a vector which transfers genetic information to another cell is typically to isolate, multiply, or express the insert in the target cell. The vector itself generally carries a DNA sequence that consists of an insert (in this case the transgene) and a larger sequence that serves as the 'backbone' of the vector. Common to all engineered vectors are an origin of replication, a multicloning site, and a selectable marker. Of these, the most commonly used vectors are plasmids. The four major types of vectors are plasmids, viral vectors, cosmids, and artificial chromosomes. A vector containing foreign DNA is termed recombinant DNA. In molecular cloning, a vector is any particle (e.g., plasmids, cosmids, Lambda phages) used as a vehicle to artificially carry a foreign nucleic sequence – usually DNA – into another cell, where it can be replicated and/or expressed.

Protein backbone versus dna