For selection of recombinants, insertional inactivation of antibiotic marker has been superseded by insertional inactivation of a marker gene coding for a chromogenic substrate. Give reasons.

Insertional inactivation of antibiotic marker:

Selection of recombinants using insertional inactivation of antibiotic markers is a tedious process. This is because it requires simultaneous plating of transformants on two different antibiotic containing mediums.

Insertional inactivation of a marker gene:

Selection of recombinants using insertional inactivation of a maker gene coding for a chromogenic substance is an easy method as it requires plating only on one antibiotic containing medium. Also, the recombinants will produce white colonies while the non-recombinants will produce colored colonies in the presence of chromogenic substrate which makes it easy to identify recombinants and non-recombinants