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E. coli is grown on medium containing a lac operon inducer and X-gal. What color will...

E. coli is grown on medium containing a lac operon inducer and X-gal. What color will the colonies be for each type? blue or white

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Answer #1

Ans) The colonies obtained will be Blue in color.

In the presence of inducer, the Lac Z gene will be transcribed and the Lac Z protein will be produced which then forms Beta-galactosidase. When X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranosidase) is present in the medium which is colorless is acted upon by the Beta-galactosidase and then the X-gal is hydrolyzed into blue colored product (5,5- Dibromo-4,4-dichloroindigo).This blue colored colonies are obtained when the plasmids are not cloned. Once the plasmids are cloned,then the insertion of DNA construct will disrupt the reading frame of lac Z gene and no lac protein will be produced and no blue colour will be produced.When the plasmids are transformed, white colonies are observed.

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