X chromatin compaction is evident at all genomic distances examined. (A) FISH probe pairs across the X chromosome. The position of YAC probes (red and white boxes) used in FISH is indicated. (B) 2D projections of 3D stacked images. Representative stained diploid nuclei of adult hermaphrodite wild type and dpy-21(e428) worms. Nuclei stained with probes pairs across the X chromosome (red and white) and counterstained with DAPI (blue) to label DNA. Scale bars equal 1 μm. (C) Boxplots indicating the distribution of 3D loci distances for wild type (n = 20) and dpy-21(e428) (n = 20) diploid nuclei. Boxes show the median and interquartile range of the data. Asterisks indicate level of statistical significance by t-test analysis (one asterisk, P <0.05; two asterisks, P <0.01; three asterisks, P <0.001).