CBSE - XII Science - Biology
can you explain me pBR322 cycle
- pBR322 was the first artificial cloning vector constructed by Bolivar and Rodriguez in 1977.
- The nomenclature of the pBR322 plasmid is as stated below: P – Plasmid, BR - Stands for Bolivar and Rodriguez who constructed this plasmid, 322 - Number given to distinguish this plasmid from the other plasmids developed in the same laboratory.
- Plasmid pBR322 has two resistance genes—ampicillin resistance (ampR) and tetracycline resistance (tetR)—which are considered useful for selectable markers. Selectable markers help in selecting those host cells which contain the transformed vectors and eliminate the non-transformants.
- Plasmid pBR322 has a variety of unique recognition sites for restriction endonucleases.
- Two unique sites—PstI and PvuI—are located within the ampR gene and BamHI and SalI are 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, which 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.
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