Question

Why is the coding sequence of an enzyme $\beta$ - galactosidase a preferred selectable marker in comparison to the ones named above?

Answer 1

The gene for the enzyme Beta-galactosidase is an alternative selectable marker. when the foreign gene is inserted within the Beta-galactosidase gene, the enzyme Beta-galactosidase gets inactivated. Then the bacteria are grown on a chromogenic substrate. Non-recombinants will produce blue-colored colonies, while recombinants will produce colorless colonies.