X-GAL (Chromogenic Substrate) CS126   5-Bromo-4-chloro-3-indolyl-beta-D-galactoside, 99+% [ 7240-90-6 ]   f.w.:408.6 daltons

X-Gal is a chromogenic substrate for ?-galactosidase that produces a rich blue color that can easily be detected visually over background. X-Gal is the substrate of choice for blue-white selection of recombinant bacterial colonies with the lac+ genotype. X-Gal is used in conjunction with IPTG.