Fig. 1. ofs mutants fail to undergo meiosis or differentiation. (A-C) Phase images, apical-tip oriented to the left. (A) Heterozygous testes appear wild-type, with elongating spermatids filling most of the testis. (B) Mutant testes lack elongating spermatids. (C) ofs/Df(3R)mbc-R1 is indistinguishable from ofs/ofs (B). (D,E) High-magnification, with diagrams of the represented stages. Color code: primary spermatocyte nucleus, red; nucleolus, black; haploid spermatid nucleus, orange; fused mitochondrial derivative, purple; dissociated mitochondria, blue; cell outlines (where discernable), gray. (D) Heterozygous testes have examples of mature primary spermatocytes (left) and onion-stage spermatids (right). (E) The most prevalent cells found in ofs testes resemble primary spermatocytes. (F,G) Whole-mount immunofluorescent images of wild-type (F, arrowhead, 2xlacZ⁺) and ofs (G, arrow, lacZ^-) clones in a heterozygous background. Flies were aged 4 days after clone induction, which allowed clones to progress midway through the meiotic G₂ of wild-type spermatocytes. (F',G') Brackets are the same size in each panel, highlighting the cell size difference between the two clones. The entire ofs cell outline (PTyr, phospho-Tyrosine) is approximately the same size as the nucleus of the control cell.