A researcher has generated recombinant E. coli cells using the pBR322 cloning vector. When these cells are plated on different media, the recombinant colonies are found to survive on a medium containing tetracycline but fail to grow on a medium containing ampicillin. Which of the following restriction endonucleases was most likely used to insert the foreign DNA into the vector?

Step-by-step solution

The recombinant cells survive on tetracycline, which means the tetracycline resistance gene ( tet^R ) is intact and functional. However, they fail to grow on ampicillin, indicating that the ampicillin resistance gene ( amp^R ) has lost its function due to insertional inactivation. Therefore, the foreign DNA must have been inserted at a restriction site located within the amp^R gene. In the pBR322 vector, the restriction sites for Pst I and Pvu I are located within the amp^R gene. Bam HI and Sal I sites are located