Fig. 3. Mosaics marked with the lacO/GFP-LacI system confirm that grk production in the oocyte is not required for oocyte AP polarity. Two foci of nuclear GFP-LacI fluorescence are visible in the oocyte nucleus (arrow), indicating that it is homozygous for the grk^2B6 allele. Multiple foci are visible in 13 nurse cell nuclei and two nuclei exhibit no foci (arrowheads). Note that GFP-LacI levels typically vary among nuclei. Though one nucleus has high GFP-LacI and some nuclei overlap in this projection of confocal optical sections, the presence or absence of foci in each nucleus was determined by inspection of individual sections at the appropriate exposure. Inset shows an enlargement of the oocyte nucleus.