AP BIOLOGY

Detailed explanation-1: -The ice-cold CaCl2 solution facilitates binding of DNA to the surface of the cell, which then enters the cell after a short period of heat-shock (3). Cells that are successfully transformed are usually identified by selection or screening markers such as drug resistance or fluorescence (4).

Detailed explanation-2: -Calcium Chloride imparts a positive charge to the cell wall. Since DNA is negatively charged molecule, the positive charge on the cell wall imparted by calcium chloride helps the DNA to get attracted towards the cell, and hence ensures a higher efficiency of successful transformants.

Detailed explanation-3: -Method. Prepare a small, overnight culture of the bacteria in LB broth. Grow at 37°C without shaking. Take a 5 mL aliquot of each transformation reaction and transfer to sterile plastic centrifuge tubes.

Detailed explanation-4: -After transformation, bacteria are selected on antibiotic plates. Bacteria with a plasmid are antibiotic-resistant, and each one will form a colony. Colonies with the right plasmid can be grown to make large cultures of identical bacteria, which are used to produce plasmid or make protein.