NEETZoologyBiotechnology - Principles and Processes
A foreign DNA fragment is ligated at the BamHI restriction site of the cloning vector pBR322. The resulting recombinant plasmids are then transformed into competent E. coli cells. Which of the following correctly describes the growth behavior of the recombinant colonies when subjected to sequential plating?
Options
- AThey will grow on both ampicillin-containing and tetracycline-containing media.
- BThey will grow on tetracycline-containing medium but fail to grow on ampicillin-containing medium.
- CThey will grow on ampicillin-containing medium but fail to grow on tetracycline-containing medium.
- DThey will fail to grow on both ampicillin-containing and tetracycline-containing media.
Correct answer
C. They will grow on ampicillin-containing medium but fail to grow on tetracycline-containing medium.
Step-by-step solution
In the cloning vector pBR322, the BamHI restriction site is located within the tetracycline resistance gene. Insertion of a foreign DNA at this site leads to insertional inactivation of the tetracycline resistance gene. As a result, the recombinant plasmids lose the ability to confer tetracycline resistance but retain ampicillin resistance. Therefore, the recombinant E. coli cells will grow on a medium containing ampicillin but will fail to grow on a medium containing tetracycline. Non-recombinant transformants wou