Enhances the mottled eye phenotype of In(1)wm4h so the eye is almost completely white and testes show patches of colourless tissue. Colourless phenotype can be suppressed by Su(var)2-11. Regions of ommatidial disorganisation are sometimes observed within white areas (interpreted as inactivation of the rst locus, located more distally that w on the In(1)wm4h rearrangement). Enhances the y variegated phenotype of Dp(1;f)1187, a higher percentage of yellow bristles are observed on the medial triple row at the anterior wing margin. Visible phenotype of Pc23 or Df(3R)red-P52 is not altered in the presence of Ubp64EEvar1.