Identify the incorrect statement. 

Insertional inactivation of $\mathrm{\beta }$-galactosidase gene leads to blue colour colonies.

In insertional inactivation, the rDNA in inserted within the coding sequence of an enzyme β-galactosidase.

Selection of recombinants due to inactivation of antibiotic is a cumbersome procedure.

Insertional inactivation of enzyme β-galactosidase leads to colourless colonies.