Transcription   of  GAL10  and  GAL1  is
   controlled  by  the (UAS[G]), which is kept constitutively open (DNase
   sensitive - free of nucleosome), by the SWI/SNF remodeling complex.

   In  the  absence  of galactose, Gal80 proteins are bound to UAS[G] via
   Gal4  proteins  so that the latter's activation domains (dark patches)
   are covered.

   Galactose  acts  as  an inducer by binding to the complex and exposing
   the activation domains, enhancing transcription.