Read the following statements regarding the selection of recombinants using a chromogenic substrate: A. The enzyme -galactosidase acts on a chromogenic substrate to produce a blue colour. B. Insertion of foreign DNA into the coding sequence of -galactosidase results in its insertional inactivation. C. Bacterial colonies having plasmids with the foreign insert produce blue coloured colonies. D. Non-recombinant colonie

Step-by-step solution

Statement A is correct. The intact -galactosidase enzyme acts on a chromogenic substrate to produce a blue-coloured product. Statement B is correct. When foreign DNA is inserted into the coding sequence of the -galactosidase gene, the gene is insertionally inactivated and loses its function. Statement C is incorrect. Bacterial colonies with the foreign insert (recombinants) have an inactivated enzyme and therefore do not produce any colour (they appear white). Statement D is incorrect. Non-recombinant colonies have