A. Ampicillin resistance gene (ampR) and tetR/ tetracycline resistance gene (tetR) are the selectable markers in the cloning vector pBR322. They help in identifying and eliminating non-transformed cells and distinguish recombinant cells from non-recombinant cells.
B. The coding sequence of an enzyme β-galactosidase, a preferred selectable marker because of simpler and easy process. In the presence of chromogenic substrate, recombinants are colourless and non-recombinants are blue in colour.
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