In genetics, pBluescript (pBS) or pBluescript II is a commercially available phagemid

Phagemid

A phagemid or phasmid is a type of cloning vector developed as a hybrid of the filamentous phage M13 and plasmids to produce a vector that can grow as a plasmid, and also be packaged as single stranded DNA in viral particles...

 containing several useful sequences for use in cloning

Cloning

Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...

 with bacteriophage

Bacteriophage

A bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...

. The sequences include a polylinker sequence (MCS), antibiotic resistance

Antibiotic resistance

Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

 sequence to ampicillin and an E. coli and f1 helper phage origin of replication

Origin of replication

The origin of replication is a particular sequence in a genome at which replication is initiated. This can either be DNA replication in living organisms such as prokaryotes and eukaryotes, or RNA replication in RNA viruses, such as double-stranded RNA viruses...

. The polylinker sequence is located within a LacZ controlled gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

 designed to provide a blue coloration when expressed in bacteria. This is usually achieved via X-gal

X-gal

X-gal is an organic compound consisting of galactose linked to a substituted indole. The compound was synthesized by Jerome Horwitz and collaborators in Detroit, MI, in 1964. The formal chemical name is often shortened to less accurate but also less cumbersome phrases such as bromochloroindoxyl...

 found in agarose growth media used to culture bacteria with pBS. If the gene is disrupted by successful insertion of a DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 sequence, the bacteria exhibit a white coloration in Blue white screening, distinguishing successful recombination from those phagemids which were not altered. These recombinant plasmids can then be used in a variety of molecular techniques. Determining expression and developing genomic libraries are some applications for which the pBS recombinants can be used.

The pBluescript cloning system is a product of Stratagene.