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Question
The image below shows the result of plating bacteria in a chromogenic medium after incorporating the gene of interest in the plasmid. Some plates had blue colonies; some plates had white colonies. A single bacterium extracted from Plate I, II, and III is shown below:
On the basis of your observations:
- Identify the plate(s) which is/are white. Give a reason.
- Identify the plate(s) which is/are blue. Give a reason.
Solution
- Plate I, the b-galactosidase enzyme is responsible for the blue colour. Gene is inserted in the b-galactosidase site of the plasmid, thereby causing insertional inactivation of the enzyme, so no blue colour is made.
- Plate II - Gene of interest not inserted in the plasmid.
Plate III - No plasmid
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