Question

Ori is some specific sequence in the vector pBR 322. Ori also has the recognition sequence for the restriction enzyme

• A. Pvu II
• B. Hind III
• C. Pst I
• D. None of the above

Answer 1

The correct option is D None of the above

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 sequences 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.

Ori is the site for origin of replication in the vector pBR 322 but it has no recognition site for any of the restriction enzymes. It cannot have any restriction sites as it will get inactivated when cut. As a result of this cleavage the plasmid will lose its property of self replication.

Any piece of DNA when linked to ori can be made to replicate within the host cells and it also controls the copy number of the linked DNA.

Hence the correct option is
d. None of the above