Hi reader ,

The insertion of rDNA into the coding sequence of an enzyme alpha-galactosidase leads to the inactivation of the enzyme called insertional inactivation. The recombinants do not produce a blue coloured colonies in the presence of chromogenic substrate while the non-recombinants produce a blue colour.

the recobinant give out white colour thus helping to differentiate between recombinants and non recombinants

i hope this helps

thank you