Question

In the recombinant DNA technology involving plasmid pBR322, insertion of foreign DNA at the PstI restriction site results in the loss of resistance against:

• A. Tetracycline
• B. Ampicillin
• C. Chloramphenicol
• D. Kanamycin

Hint:

Important restriction sites in pBR322:
• PstI \(\rightarrow\) ampicillin resistance gene
• BamHI and SalI \(\rightarrow\) tetracycline resistance gene Insertion inside a resistance gene causes insertional inactivation.

Answer 1

The Correct Option is B

Concept: pBR322 is one of the most commonly used plasmid vectors in recombinant DNA technology. Important features of pBR322 include:
• Origin of replication (ori)
• Ampicillin resistance gene (amp^R)
• Tetracycline resistance gene (tet^R)
• Multiple restriction sites The PstI restriction site is located within the ampicillin resistance gene.

Step 1: Understanding insertional inactivation. When foreign DNA is inserted into the PstI site:
• the ampicillin resistance gene becomes disrupted
• bacteria lose resistance to ampicillin This phenomenon is called insertional inactivation.

Step 2: Identifying the correct antibiotic resistance lost. Since PstI lies inside the ampicillin resistance gene: \[ \boxed{\text{Ampicillin resistance is lost}} \] Final Answer: \[ \boxed{(B)\ \text{Ampicillin}} \]