Chromosome Conundrum The three-dimensional organization of chromosomal DNA within the cell nucleus plays an important role in gene regulation. Naumova et al. (p. 948 , published online 7 November; see the Perspective by Kleckner et al. ) used chromosome conformation capture-based methods in human tissue culture cells to analyze the higher order folding of human chromosomes across the cell cycle. During interphase the chromosomes showed locus-specific compart-mentalization. In mitotic cells, on the other hand, the chromosome organization was more linear, consistent with arrays of consecutive chromatin loops.