Question

In pBR 322 for tetracycline resistance gene has a recognition site for which of the
following restriction endonuclease?
A. Hind 111
B. BamH1
C. EcoR1
D. Pst1

Answer 1

Hint: pBR 322 is the artificially reconstructed plasmid from the plasmid of the E.Coli bacteria. The cloning vector or plasmid vector pBR 322 contains two resistance genes. These are ampicillin resistance and other tetracycline resistance genes.

Complete Answer:
- pBR 322 is a small molecule DNA which is completely separated from chromosomal DNA.
- Restriction enzymes are the enzymes that can cut the foreign DNA. pBR 322 has several restriction sites for the restriction enzymes like Hind 111, EcoR 1, BamH 1, Sal 1, Pvu 11, Pst 1, Cla 1, etc. It also has antibiotic resistance genes for ampicillin and tetracycline along with an ORI site, which is the site of replication. Rop gene present in pBR 322 codes for the proteins involved in the replication of the plasmid.
- BamH 1 site for the restriction enzyme is present on the gene for tetracycline resistance.
Pvu 1 and Pst 1 sites are located on the ampicillin resistance gene in pBR 322. So by the action of BamH 1, tetracycline resistance of the plasmid will be altered. Recombinant plasmid loses tetracycline resistance due to the insertion of foreign DNA but can be selected by plating transformants for an ampicillin containing medium.

Hence the correct option is B.

Note: pBR322 was created in 1977 in San Francisco and widely used as a cloning vector. It was prepared by two scientists named Bolivar and Rodriguez. P stands for plasmid, B stands for Bolivar and R stands for Rodriguez in pBR 322. It is regarded as the workhouse of the gene cloning laboratory that contains ORI, tetR and ampR.