NEET2026BiologyChapterActual
Observe the schematic representation of the cloning vector pBR322 given below. If a foreign DNA fragment is successfully ligated at the PvuI restriction site, which of the following correctly describes the growth characteristics of the resulting recombinant E. coli cells?
Options
- AThey will grow on a medium containing ampicillin but fail to grow on a medium containing tetracycline.
- BThey will grow on a medium containing tetracycline but fail to grow on a medium containing ampicillin.
- CThey will grow normally on media containing both ampicillin and tetracycline.
- DThey will fail to grow on both ampicillin and tetracycline containing media.
Correct answer
B. They will grow on a medium containing tetracycline but fail to grow on a medium containing ampicillin.
Step-by-step solution
Based on the schematic representation of the cloning vector pBR322, the restriction site for the enzyme PvuI is located within the ampicillin resistance gene ( amp^ R ). When a foreign DNA fragment is successfully ligated at the PvuI site, it disrupts the amp^ R gene. This phenomenon is known as insertional inactivation. As a result, the recombinant plasmid loses its ability to confer resistance to ampicillin. However, the tetracycline resistance gene ( tet^ R ) remains intact and functional because no insertion oc