Fig. 1. Gug mutations act as dominant suppressors of a tsh reporter gene in the eye. (A,B) Heterozygotes for P(Lac w⁺)tsh^J834 (B is also heterozygous for the Gug^S2 mutation). (A) Note that the white gene is active in anterior cells of the eye (Sun et al., 1995) as is the tsh gene; (B) expression of these genes is reduced.