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A researcher constructs a recombinant plasmid containing an intact ampicillin resistance gene ( amp^ R ) but accidentally introduces a mutation that completely inactivates its origin of replication ('ori'). This plasmid is then transformed into competent, ampicillin-sensitive E. coli cells. If these cells are subsequently plated on an agar medium containing ampicillin, what will be the most likely observed result aft

Options

  1. ANormal colonies will appear because the ampicillin resistance gene is intact.
  2. BColonies will appear but they will lack the gene of interest.
  3. CThe bacteria will undergo lysis immediately upon transformation.
  4. DNo colonies will appear on the plate because the plasmid cannot multiply and be maintained in the progeny cell

Correct answer

D. No colonies will appear on the plate because the plasmid cannot multiply and be maintained in the progeny cell

Step-by-step solution

The origin of replication ('ori') is a specific DNA sequence responsible for initiating replication. Any piece of DNA linked to this sequence can be made to replicate within the host cells. If the 'ori' is inactivated, the plasmid cannot replicate independently. Even though the plasmid carries an intact ampicillin resistance gene, it will not be duplicated when the host cell divides. Consequently, the plasmid will be diluted and lost in the progeny cells, leaving them sensitive to ampicillin. Therefore, the cells w

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