Blue-white screening

Definition

Blue-white screening is a molecular biology technique used to identify recombinant bacteria. It distinguishes between colonies with and without plasmid inserts based on color changes in the presence of X-gal.

5 Must Know Facts For Your Next Test

1. Blue-white screening relies on the disruption of the lacZ gene by an inserted DNA fragment.
2. X-gal is a chromogenic substrate that turns blue when cleaved by β-galactosidase, indicating non-recombinant colonies.
3. White colonies indicate successful insertion of foreign DNA into the plasmid vector, disrupting β-galactosidase activity.
4. The technique requires competent cells transformed with a plasmid containing the lacZ gene and an antibiotic resistance marker.
5. IPTG is often used in conjunction with X-gal to induce expression of the lac operon.

Related terms

Plasmid Vector: A circular DNA molecule used as a tool for cloning and transferring genetic material.

Lac Operon:

A set of genes involved in lactose metabolism, regulated by the lac repressor and activator proteins.

Competent Cells: Bacterial cells treated to allow uptake of foreign DNA during transformation.