NEETZoologyBiotechnology - Principles and Processes
A recombinant pBR322 plasmid is constructed by inserting a foreign DNA fragment at the Pst I restriction site. If this recombinant plasmid is successfully transformed into E. coli cells, what will be the growth characteristics of these transformants on antibiotic-containing media?
Options
- AThey will grow on an ampicillin-containing medium but not on a tetracycline-containing medium.
- BThey will grow on a tetracycline-containing medium but not on an ampicillin-containing medium.
- CThey will fail to grow on both ampicillin and tetracycline-containing media.
- DThey will grow on both ampicillin and tetracycline-containing media.
Correct answer
B. They will grow on a tetracycline-containing medium but not on an ampicillin-containing medium.
Step-by-step solution
In the pBR322 cloning vector, the restriction site for Pst I is located within the amp^R (ampicillin resistance) gene. When a foreign DNA fragment is inserted at the Pst I site, it causes insertional inactivation of the amp^R gene. As a result, the recombinant plasmid loses ampicillin resistance but retains tetracycline resistance (since the tet^R gene remains intact). Therefore, the transformants containing the recombinant plasmid will be able to grow on a tetracycline-containing medium but will fail to grow on an