Question

Blue white selection is used
A. To treat for the presence of a plasmid in bacteria
B. To reveal the identity of a cloned DNA fragment
C. To express the product of a cloned gene
D. To test the presence of a cloned insert in a plasmid

Answer 1

Hint: The blue-white screen is one of the screening techniques that provides a way to find the recombinant microbes in vector-based molecular cloning experiments. It is a kind of rapid test and is enlightened by biochemistry utilising equipment and vectors for cloning molecular atoms. This type of technology is found in biotechnology.

Complete step-by-step answer:
Blue-white screening offers an appropriate and effective method to differentiate bacterial colonies. Recombinant DNA technology includes a few steps in a certain order like isolation of the desired DNA fragment, transferring the recombinant DNA into the host, ligation of the DNA fragment into a vector, fragmentation of DNA by restriction endonucleases, isolation of DNA, culturing the host cells in a medium at large scale and extraction of the required product. The blue-white screen is a screening method that allows for quick and easy detection of recombinant bacteria in such experiments. Recombinant DNA is inserted into a competent host cell feasible for conversion, which is then developed in presence of X – gal. Cells converted with non-recombinant plasmids (i.e. only the vector) grow into blue colonies and a cell converted with vectors that contain Recombinant DNA will generate white colonies. This technique of screening is generally carried out with an appropriate bacterial strain, but other organisms like yeast may also be used.
Hence the correct answer is option d.

Note: Blue-white screening of bacterial colonies is a prevalent and efficient molecular biological tool. This technique is based upon the inspectional inactivation of the lac-z gene that exists on the vector.