chromogen / chromogene [ˈkro:məʤɛn]
chromogen – n. – 1 (Bioch.) a precursor (as urobilinogen) of a pigment (as urobilin); 2. a compound containing a chromophore ATH is not itself a dye but is capable of becoming one on introduction of an auxochromic group into the molecule; 3. a pigment producing microorganism (i.e. many bacteria)
chromogene – n. – gene, used to distinguish the nuclear gene from the cytogene in an otherwise ambiguous context