Choosing a Cloning Vector

互联网2014-02-13

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Since the construction of the first generation of general cloning vectors in the early 1970s, the number of plasmids created has increased to an almost countless number. Thus, a critical decision facing today’s investigator is that of which plasmid to use in a particular project? Despite the bewildering choice of commercial and other available vectors, the choice of which cloning vector to use can be decided by applying a small number of criteria: insert size, copy number, incompatibility, selectable marker, cloning sites, and specialized vector functions. Several of these criteria are dependent on each other. This chapter discusses these criteria in the context of choosing a plasmid for use as a cloning vector and Table 1 displays the features of some commonly used cloning vectors.

Table 1 Commonly Used Cloning Vectors

		Commercial source
Plasmid	Features
pUC18, pUC19	Small size (2.7 kb)	NEB
	High copy number
	Multiple cloning site
	Ampicillin-resistance marker
	Blue/white selectionsee Chapter 19)
pBluescript vectors	As pUC	Stratagene
	Single-stranded replication origin
	T7 and SP6 promoters flanking MCS^a
pACYC vectors	Low copy number (15 copies per cell)	NEB
	p15A origin of replication
Supercos	Cosmid vector	Stratagene
	Two cos sites
	Insert size 30–42 kb
	Ampicillin-selectable marker
	T3 and T7 promoters flanking cloning site
EMBL3	λreplacement vector	Promega
	MCS sites: Sal I, Bam HI and Eco RI
λZAP	λ vector	Stratagene
	In vivo excision into pBluescript phagemid vector
	Cloning capacity 10 kb
	Blue/white selection
pBeloBAC11	BAC vector	NEB
	Inserts up to 1 Mb
	T7 and SP6 promoters flank insertion site
	Blue/white selection
	Cos site
	LoxP site

^a MCS = multiple-cloning site.