Insertion of a foreign DNA at BamHI site in an E. coli cloning vector pBR322 results in the loss of antibiotic resistance towards :

(C) Tetracycline
The cloning vector pBR322 contains two antibiotic resistance genes: ampicillin resistance ( \(a m p^R\) ) and tetracycline resistance \(\left(\right.\)tet\(\left.^R\right)\).
The restriction site for the enzyme BamHI is located within the tetracycline resistance gene \(\left(\right.\)tet\(\left.^R\right)\).
When a foreign DNA is inserted at the BamHI site, the \(\left(\right.\)tet\(\left.^R\right)\) gene gets interrupted. This phenomenon is known as insertional inactivation.
Due to this insertional inactivation, the recombinant plasmid loses its ability to confer resistance against tetracycline, while the ampicillin resistance gene remains intact and functional.