what do bacterial cells need in order for blue-white screening to work?

Expert Solution

Schematic representation of formation of white colonies in blue white screening test.

Blue -white screening is a technique for the identification of recombinant bacteria .

In this procedure ,the lac z gene is inserted in the plasmid vector .
The enzyme beta -galactosidase is encoded by the lac z gene.The enzyme hydrolyzes a synthetic chromogenic substrate X-gal ,releases the substituted indole and give ,intensely blue product .(X gal is hydrolyzed to form 5-bromo-4-chloro -indoxyl which dimerizes to produce 5,5'-dibromo -4,4'-dichloro indigo )
IPTG is used along with X gal. It is an inducer for blue - white screening.
Here a foreign gene is introduced in to lac Z ,the gene will be deactivated .Hence no blue colour will develop ,as beta -galactosidase is not produced due to insertional inactivation .(deactivation of lac -Z).
A plasmid vector with inserted foreign gene, X gal, IPTG , competent E coli are required for this test.

gladiator answered 1 year ago

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