Question

From the following, which is not a characteristic feature of the vector pBR322?

• A. It has two antibiotic-resistance genes: amp^R and tet^R.
• B. It was the first artificial cloning vector constructed in 1997 by Boliver and Rodriguez.
• C. The ampicillin-resistance gene has restriction sites for BamHI and SalI
• D. The restriction site for Pvu II is present in the replication of plasmid (rop) gene.

Answer 1

Answer: (C)

pBR322 was the first artificial cloning vector constructed by Bolivar and Rodriguez in 1977.
In pBR322, p refers to plasmid; BR refers to Bolivar and Rodriguez, the scientists that constructed this plasmid; 322 refers to the number given to distinguish this plasmid from the other plasmids developed in the same laboratory.
Plasmid pBR322 contains two resistance genes, namely ampicillin resistance (ampR) gene and tetracycline resistance (tetR). These resistance genes are used as selectable markers. Besides this, plasmid pBR322 has a variety of unique recognition sites for restriction endonucleases.
Two unique sites, i.e., PstI and PvuI, are located within the ampR gene, whereas BamHI and SalI, are located within the tetR gene.
Insertion of the DNA fragment into the plasmid using enzyme PstI or PvuI places the DNA insert within the gene ampR makes ampR non-functional. Bacterial cells containing such a recombinant pBR322 will be unable to grow in the presence of ampicillin but will grow on tetracycline.
Insertion of the DNA fragment into the plasmid using enzyme BamHI and SalI places the DNA insert within the gene tetR makes tetR non-functional. Bacterial cells containing such a recombinant pBR322 will be unable to grow in the presence of tetracycline but will grow on ampicillin.