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Biochemistry

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Purines, Pyrimidines and Nucleic Acid Metabolism

Question
47 out of 59
 

Blue-white Color Screen technique is Used In DNA Cloning For? (AIIMS May 2011)



A To detect host DNA

B To Screen for recombinant vectors

C To find out the new cloned fragment of DNA

D To find out the plasmid incorporated in DNA

Ans. C To find out the new cloned fragment of DNA

a. The vector may also include a gene spanning the cloning site which creates an easily detectible phenotype to allow for selection of inserts, such as for example the LacZα gene which is used to span a cloning site to allow for convenient blue-white color screening for recombinant vectors which include an insert at the site within the LacZα gene.

b. The blue-white screen is a molecular technique that allows for the detection of successful ligations in vector-based gene cloning.

c. DNA of interest is ligated into a vector. The vector is then transformed into competent cell (bacteria). The competent cells are grown in the presence of X-gal.

d. If the ligation was successful, the bacterial colony will be white; if not, the colony will be blue.

e. This technique allows for the quick and easy detection of successful ligation, without the need to individually test each colony.

f. The manual enzymatic method (Sanger) employs specific dideoxynucleotides that terminate DNA strand synthesis at specific nucleotides as the strand is synthesized on purified template nucleic acid

Purines, Pyrimidines and Nucleic Acid Metabolism Flashcard List

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