In the above represented plasmid an alien piece of DNA is inserted at the EcoRI site. Which of the following strategies will be chosen to select the recombinant colonies?
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In the blue/white screening method, the recombinant colonies are white because the insertion of foreign DNA disrupts the beta-galactosidase gene, preventing the conversion of X-gal to a blue color.
Using ampicillin \& tetracyclin containing medium plate.
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The Correct Option isB
Solution and Explanation
The plasmid carries the beta-galactosidase gene, part of the LacZ system. Insertion of foreign DNA occurs at the EcoRI restriction site. Insertion into the LacZ gene disrupts its function, inhibiting beta-galactosidase production. Beta-galactosidase normally converts X-gal into a blue product.
- Colonies with inserted foreign DNA will appear white due to LacZ disruption.
- Colonies without inserted foreign DNA will retain an intact LacZ gene and appear blue.
Therefore, recombinant colonies (containing foreign DNA) will be white. The optimal strategy involves selecting white colonies.
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