Question

If a plasmid is having two antibiotic resistant genes, say ampicillin resistant and chloramphenicol resistant. If the plasmid grows in ampicillin containing medium but not in chloramphenicol, what can be concluded?

• A. The insert is not present in any of the gene
• B. The insert is present in ampicillin gene but not in chloramphenicol gene
• C. The insert is present in chloramphenicol gene but not in ampicillin gene
• D. The insert is present between both of the gene

Hint:

When analyzing plasmids with multiple resistance genes, growth in one antibiotic medium but not another often indicates a disrupted resistance gene due to the insert.

Answer 1

The Correct Option is B

Step 1: Understanding the plasmid behavior.
The plasmid contains genes for resistance to ampicillin and chloramphenicol. If it grows in an ampicillin-containing medium but not in chloramphenicol, it suggests that the plasmid has an insert disrupting the chloramphenicol resistance gene.
Step 2: Analyzing the options.
(1) The insert is not present in any of the gene: This is incorrect because the plasmid is growing in the ampicillin medium, indicating that the ampicillin resistance gene is functional.
(2) The insert is present in ampicillin gene but not in chloramphenicol gene: Correct — The insert likely disrupts the chloramphenicol resistance gene, while leaving the ampicillin resistance gene intact.
(3) The insert is present in chloramphenicol gene but not in ampicillin gene: This is incorrect because the plasmid can still grow in ampicillin-containing media, indicating the ampicillin gene is functional.
(4) The insert is present between both of the gene: This is incorrect because the plasmid grows in ampicillin-containing media, so the ampicillin gene is likely not disrupted.
Step 3: Conclusion.
The correct answer is (2) The insert is present in ampicillin gene but not in chloramphenicol gene, as the plasmid grows only in ampicillin medium.