Figure 2 .

Immuno-FISH of metaphase arrested oocytes. Oocytes from experimental females from the indicated lines are shown; each was FM7/y w; ald^excision/Df(3R)AN6; pol. For each image, the tubulin spindle (antibody) is shown in gray, DNA (DAPI) in blue, the 4 (FISH probe) in red, and the X (FISH probe) in green. All bars, 4 µm. Small and variable foci of both probes can be found on other chromosomes (Hughes et al. 2009) so the size of the block of probe signal is needed to determine chromosome locations. (A) An ald^excision-14 oocyte showing proper coorientation of both X and 4. FM7 is facing the right pole. (B) An ald^excision-1 oocyte showing proper X coorientation and both 4 chromosomes oriented to the left pole. The left X mass is the distal FM7 signal, with its centromeric spot on top of the combined 4 signal. (C) An ald^excision-4 oocyte showing proper coorientation of both 4 chromosomes with both X chromosomes oriented to the left pole. (D) An ald^excision-23 oocyte showing heterologous segregation, with both 4 chromosomes oriented to the left pole and both X chromosomes oriented to the right. (E) An ald^excision-15 oocyte showing nonheterologous segregation, with all four X and 4 homologs facing the right pole.