Question

In insertional inactivation of $\beta$-galactosidase gene, the bacteria in white colonies have

• A. Non- recombinant plasmid
• B. Recombinant plasmid
• C. No plasmid
• D. Linear foreign DNA

Answer 1

The correct option is B Recombinant plasmid

• Blue-white screening technique allows rapid detection of recombinant bacteria in the cloning experiments.
• The desired gene is inserted into Ti plasmid vector and then transferred into the cells which are competent for transformation.
• These cells are grown in the presence of X-gal which is a chromogenic substance.
• Cells transformed with vectors containing recombinant DNA will produce white colonies and the cells transformed with non-recombinant plasmids (i.e., only the vector) grow into blue colonies.

Thus, the correct answer is option B.