The plasmid pBR322 carries which antibiotic resistance marker genes that are routinely used for selection and insertional inactivation?

Introduction / Context:
pBR322 is among the most historically important E. coli plasmid vectors. Knowing its selectable markers is foundational for understanding classic cloning strategies, especially insertional inactivation screens using the Amp^r and Tet^r loci.

Given Data / Assumptions:

• pBR322 contains bla (Amp^r) and tet (Tet^r) genes.
• Multiple cloning sites can disrupt Tet^r for insertional inactivation.
• Selection often starts with Amp^r, followed by replica plating to test Tet^r.

Concept / Approach:
Transformants are selected on ampicillin plates (Amp^r). Recombinants with inserts in the tet region lose tetracycline resistance, allowing discrimination between recombinant and non-recombinant clones via replica plating. This dual-marker system illustrates early cloning logic before modern blue–white screening became dominant.

Step-by-Step Solution:

Verification / Alternative check:
Standard plasmid maps confirm bla and tet loci on pBR322, with defined restriction sites used historically for insertional inactivation.

Why Other Options Are Wrong:

• A/B/D/E: Each lists only one or a different marker set, not matching the canonical pBR322 features.

Common Pitfalls:
Confusing pBR322 with pUC plasmids, which carry Amp^r and lacZα for blue–white screening rather than Tet^r.

Final Answer:
Both ampicillin resistance (Amp^r) and tetracycline resistance (Tet^r)