Insertion of a foreign DNA at BamHI site in an E. coli cloning vector pBR322 results in the loss of antibiotic resistance towards :
- Ampicillin and tetracycline
- Ampicillin
- Tetracycline
- Gentamycin
Answer
(3) Tetracycline
Solution
As per NCERT, pBR322 carries two antibiotic resistance genes: ampR (ampicillin) and tetR (tetracycline).
The BamHI site lies within the tetracycline resistance gene (tetR).
⇒ Insertion of foreign DNA at this site inactivates tetR (insertional inactivation).
∴ The recombinant plasmid loses tetracycline resistance but still shows ampicillin resistance.
Answer: (3)