Question

(a) Name the selectable markers in the cloning vector pBR322? Mention the role they play.
(b) Why is the coding sequence of an enzyme β - galactosidase a preferred selectable marker in comparison to the ones named above?

Answer 1

Hint: The selectable marker could be a gene which is present within the vector which when introduced into the host, or cells in culture, ends up in a trait which is suitable for the aim of artificial selection. The selectable markers are generally antibiotic resistance genes. These help within the process of artificial selection. They also help in identification of the transformants and permit selectively to grow but also eliminate the non-transformants.

Complete answer:
(a)In the cloning vector pBR322, the selectable markers are ampicillin and tetracycline resistance genes. The role they play within the selection of transformed cells from non-transformed cells is that they support. They also help to differentiate between recombinant cells and non-recombinant cells.

(b)An alternative selectable marker is that the gene for the β -galactosidase enzyme. when the foreign gene is incorporated into the β -galactosidase gene, the enzyme β -galactosidase gets inactivated. The bacteria on a chromogenic substrate are then grown. Non-recombinants will create colonies with blue colors, while colorless colonies are formed by recombinants.

Note: When antibiotic resistance and β-galactosidase are used together for selection, the double-selection scheme cuts down on the work required to check the experiment. Out of the countless bacteria on the plate, and many growing colonies that have obsessed a plasmid, only some dozen white colonies originate from single bacteria containing recombinant plasmids and want to be further examined. Other studies can show whether there's a gene of interest in recombinant inserts.