Question

The diagram given below represents the image of the cloning vector pUC 18. The gene of interest is inserted and ligated within the gene lacZ. The recombinant DNA is introduced in the host bacterial cell. Explain the method that would help in selection of recombinant colonies from non-recombinant colonies.

Answer 1

Blue-white selection

LacZ codes for β-galactosidase

The product (β-galactosidase) becomes inactive due to insertion of foreign protein (coded by foreign gene).

Chromogenic substrate converted into blue coloured product in non-recombinant colonies, remains colourless in recombinant colonies.