AP BIOLOGY

Detailed explanation-1: -For screening the clones containing recombinant DNA, a chromogenic substrate known as X-gal is added to the agar plate. If -galactosidase is produced, X-gal is hydrolyzed to form 5-bromo-4-chloro-indoxyl, which spontaneously dimerizes to produce an insoluble blue pigment called 5, 5’-dibromo-4, 4’-dichloro-indigo.

Detailed explanation-2: -Tips for blue-white screening All colonies on this plate should be blue, indicating that your IPTG and x-gal are working as they should be.

Detailed explanation-3: -Blue-white screening of bacterial colonies is a popular and effective molecular biology tool often used to detect recombinant bacteria in cloning experiments. Central to this technique is the enzymatic activity of -galactosidase, a tetrameric enzyme encoded by the lacZ gene in E.

Detailed explanation-4: -The presence of a promoter is necessary when screening techniques such as blue-white selection are used. Cloning vectors without promoter and RBS for the cloned DNA sequence are sometimes used, for example when cloning genes whose products are toxic to E. coli cells.

Detailed explanation-5: -Blue-white screening provides a convenient and powerful way to distinguish bacterial colonies or phage plaques that contain a cloning vector with a DNA insert, from those containing empty vectors with no insert DNA.