Chromatin Structure Simulator

DNA does not float loose inside a nucleus — it is wound, coiled and re-coiled through a hierarchy of packaging levels so that roughly two metres of double helix fits inside a compartment a few micrometres wide. This simulator morphs a single simulated strand through that hierarchy: a bare double helix wraps into nucleosome "beads on a string", the beaded chain coils into the 30-nm solenoid fibril, and the fibril condenses further into a mitotic-chromosome-like rod, with the real approximate compaction ratio shown at each stage. A second control switches the same fibril between open euchromatin and densely packed heterochromatin, and tracks how that switch changes whether a marked gene locus stays reachable by the transcription machinery or gets buried out of reach — a simplified but concrete picture of epigenetic gene silencing.