Question

In pBR322, how many common recognition sites are present?

• A. 7
• B. 8
• C. 3
• D. 4

Answer 1

The correct option is B 8

pBR322 is a plasmid and was one of the first widely used Escherichia coli cloning vectors used to create recombinant DNA and obtain multiple copies of the alien gene. It is named after Bolivar and Rodriguez.

Common features of pBR322 are as follows:

• Restriction sites - It has multiple restriction sites for different restriction enzymes such as Pvu II, Pvu I, BamH I, EcoR I, Hind III, Pst I, Sal I, Cla I, etc.
• Rop - It is a specific base sequence that codes for the rop protein involved in the replication of the plasmid.
• Selectable markers - It has two selectable markers, one for ampicillin resistance amp^R and one for tetracycline resistance tet^R .
• Ori - It has an ori site or origin of replication site. Any piece of DNA when linked to this sequence can be made to replicate within the host cells.

Pictorial representation of pBR322

Figure : pBR322

Recognition sites are specific nucleotide sequences, present on the vector DNA, that can be recognised and cleaved by restriction endonucleases for incorporation of the gene of interest. pBR322 has 8 common recognition sites.

Hence the correct option is
a. 8