Fig. 4. EGFP-Tomb rescues the tomb meiotic-arrest mutant, and localises to chromatin in wild-type primary spermatocytes. (A,B) Phase contrast of wild-type (A) and tomb^GS12862 (B) testes. Primary spermatocytes occupy most of the apical end. Elongating spermatid bundles are seen inside, and spilling out from, the wild-type testis, whereas tomb^GS12862 testes contain only stages up to mature primary spermatocytes. (C,D) EGFP-Tomb expression rescues the tomb meiotic-arrest defect; extensive spermatid elongation is apparent (D, arrows). (E-H) EGFP and phase contrast of Bam-Gal4-VP16, UAS-EGFP-Tomb testes. The driver promotes strong expression in early primary spermatocytes (E,F); expression declines as spematocytes mature (G,H). In primary spermatocytes, EGFP-Tomb was predominantly chromatin associated: each nucleus had three prominent labelled regions corresponding to the major chromosome bivalents (G, arrows).