The blue and white selectable markers have been developed which differentiate recombinant colonies from non-recombinant colonies on the basis of their ability to produce colour in the presence of a chromogenic substrate. Given below are two statements about this method: Statement I : The blue coloured colonies have DNA insert in the plasmid and they are identified as recombinant colonies. Statement II : The colonies

Step-by-step solution

Statement I is incorrect but statement II is correct as a recombinant DNA is inserted within the coding sequence of an enzyme, -galactosidase. This results into inactivation of the gene for synthesis of this enzyme. Thus, presence of insert results into insertional inactivation of the -galactosidase gene and the colonies do not produce any colour and identified as recombinant colonies. Whereas non-recombinant transformants will produce blue colour in presence of chromogenic substrate.