Genome Packing: DNA to Chromosome

The human genome's roughly 6.4 billion base pairs form about 2 metres of DNA double helix that has to fit inside a cell nucleus only a few micrometres wide. This simulator renders that packing problem as an interactive 3D model of the real hierarchy of DNA compaction: the bare double helix, nucleosomes strung like beads on a string, their further coiling into the 30 nm chromatin fiber, looped domains anchored to a protein scaffold, and finally the tightly coiled metaphase chromosome visible under a microscope during cell division. Drag the level slider (or jump with the preset buttons) to morph continuously between these five stages while live readouts track the compaction ratio, fiber diameter and the packaged length a real 200,000 base-pair stretch of DNA would occupy at each level, and a second slider lets you see how the biological linker-DNA length between nucleosomes changes the packing.