IPTG (isopropyl b-D-1-thiogalactopyranoside) X-gal (5-bromo4-chloro-3-indolyl-b-D-galactopyranoside). When acted on by that enzyme, X-gal releases a blue color that makes it useful as substrate in assays.
#Unit 2. Cellular Organization#Lac Operon#Part B Pointers