Question

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

• A. Nonrecombinant 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 a 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.

So the correct answer is option B.