AP BIOLOGY

Detailed explanation-1: -After a short incubation in ice, a mixture of chemically competent bacteria and DNA is placed at 42°C for 45 seconds (heat shock) and then placed back in ice. SOC media is added and the transformed cells are incubated at 37°C for 30 min with agitation.

Detailed explanation-2: -The two most popular methods of bacterial transformation are (1) heat shock of chemically prepared competent cells (chemical transformation), and (2) electroporation of electrocompetent cells.

Detailed explanation-3: -Transformation is a key step in DNA cloning. It occurs after restriction digest and ligation and transfers newly made plasmids to bacteria. After transformation, bacteria are selected on antibiotic plates. Bacteria with a plasmid are antibiotic-resistant, and each one will form a colony.

Detailed explanation-4: -Bacterial strains and plasmids coli DH5 was used as the cloning host for propagation of expression vector. Three different E. coli expression strains BL21(DE3), Rosetta-gami and SHuffle T7 were prepared and transformed using the standard protocols. pET-21a was used as the expression vector.