Single step blue-white screening of non-recombinant and recombinant is possible by using selectable marker
Bt gene
tet gene
lac Z gene
cry gene
Answers
Single-step blue-white screening of non-recombinant and recombinant is possible by using a selectable marker: lac Z gene.
Explanation:
The vector pUC18 has a gene lac Z gene that synthesises beta-galactosidase which is a 1024 aa long chain. These beta-galactosidase act on X-gal which is a chromogenic substance present in bacterial cell culture media. The blue colour is produced when beta-galactosidase reacts with X-gal.
When insertion is done in the lac Z gene, the sequence for the synthesis of beta-galactosidase is disrupted. Hence no beta-galactosidase is formed. Hence no reaction occurs beta-galactosidase and x-gal, no blue colour is formed instead white colour is observed.
When screening is done, one can easily differentiate between recombinants and non-recombinants.