Visualization of C. elegans extrachromosomal arrays by GFP. One to two bright spots are seen per nucleus when the fusion proteins are bound to the lacO array. If the fusion proteins remain unbound, then the nucleus has diffuse fluorescence (arrowheads). If fusion proteins bind to the lacO array then the nucleus have localized bright spots (arrows). (A) Embryos: dpy-20; syEx [pMH86, pPD49-78::GFP-LacI, lacO] embryos were mounted on 5% Noble agar and examined under Nomarski optics and epifluorescence at 100 X. (B) A confocal photomicrograph of a syIs44 L4 hermaphrodite pharynx.