In the above represented plasmid an alien piece of DNA is inserted at EcoRI site. Which of the follo

Question

In the above represented plasmid an alien piece of DNA is inserted at EcoRI site. Which of the following strategies will be chosen to select the recombinant colonies?

Professor PC Thomas Classes · Answer

(a) : The insertion of alien piece of DNA at EcoRI site in the given plasmid, will lead to the insertional inactivation. In this, an alien piece of DNA is inserted within the coding sequence of an enzyme, $\beta$-galactosidase. This results into inactivation of the gene for synthesis of this enzyme and the colonies do not produce any colour. These colonies are marked as recombinant colonies. If the plasmid in the bacterium does not have an insert, i.e., is non-recombinant, the presence of chromogenic substrate gives blue coloured colonies.