Plasmid pBR322 has PsI restriction enzyme site within gene ampR that confers ampicillin resistance. If this enzyme is used for inserting a gene for β-galactoside production and the recombinant plasmid is inserted in a E.coli strain
Answer: (C) it will not be able to confer ampicillin resistance to the host cell. Answer: (C) it will not be able to confer ampicillin resistance to the host cell Solution: The Pst I site lies within the ampR gene; inserting a foreign gene at a restriction site inside an antibiotic-resistance gene causes insertional inactivation of that gene (NCERT illustrates this with the BamH I site inside the tetracycline-resistance gene of pBR322).
- A.it will lead to lysis of host cell.
- B.it will be able to produce a novel protein with dual ability
- C.it will not be able to confer ampicillin resistance to the host cell✓
- D.the transformed cells will have the ability to resist ampicillin as well as produce β-galactoside
Correct Answer
(C) it will not be able to confer ampicillin resistance to the host cell
Solution & Explanation
Answer: (C) it will not be able to confer ampicillin resistance to the host cell Solution: The Pst I site lies within the ampR gene; inserting a foreign gene at a restriction site inside an antibiotic-resistance gene causes insertional inactivation of that gene (NCERT illustrates this with the BamH I site inside the tetracycline-resistance gene of pBR322). Hence the recombinant plasmid loses ampicillin resistance and cannot confer it to the host. It does not lyse the host or produce a fused dual-function protein. NCERT Reference: Ch 9, p.169, line(s) 42-43 — "The recombinant plasmids will lose tetracycline resistance due to insertion"