Question

In blue–white screening, what do the white colonies indicate?

Options

• Recombinant colonies with a disrupted beta-galactosidase gene

• Non-recombinant colonies with an intact beta-galactosidase gene

• Cells that have developed spontaneous resistance to ampicillin

• Non-transformant bacterial cells lacking the plasmid vector

Answer 1

In blue–white selection, the insertion of foreign DNA disrupts the beta-galactosidase gene. A disrupted gene results in recombinant white colonies, whereas an intact gene forms blue colonies (non-recombinants).