Biotechnology- Principles and Processes Question 10
10. The two antibiotic resistance genes on vector pBR322 are for
(a) Tetracycline and Kanamycin
(b) Ampicillin and Tetracycline
(c) Ampicillin and Chloramphenicol
(d) Chloramphenicol and Tetracycline
Show Answer
Answer : b
Hints & Solutions
(b) E.coli cloning vector pBR322 contains antibiotic resistance genes for Ampicillin (ampR) and Tetracycline (tetR) as 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 nonfunctional. Bacterial cells containing such a recombinant pBR322 will be unable to grow in the presence of ampicillin but will grow on tetracycline
