AP BIOLOGY

Detailed explanation-1: -After the introduction of r-DNA into a suitable host cell, it is essential to identify those cells which have received the r-DNA molecule. This process is called screening. After the introduction of r-DNA into a suitable host cell, it is essential to identify those cells which have received the r-DNA molecule.

Detailed explanation-2: -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-3: -A screen will help you more easily identify successful clones so you have to weed through fewer colonies after your experiments. As a common example, a selection will leave you with the colonies that contain your plasmid backbone, as it often relies on antibiotic resistance.

Detailed explanation-4: -Screening can be based on detecting the DNAsequence of the. cloned gene. A copy of a gene that has been combined with a plasmid and placed into a bacteria cell., detecting a protein that the gene encodes, or the use of linked DNA markers.