In this computer model, a cross-section of a condensed chromosome shows large loops of DNA (rainbow colors) bundled into smaller loops and held together by rings of condensin protein (center, dark blue and red). Credit: Images made by Anton Goloborodko and Johan Gibcus, with input from Kumiko Samejima, Bill Earnshaw, Leonid Mirny and Job Dekker.
Condensin II (red rings) generates long loops of chromosomes, and forms a helical scaffold for the loops to pack around. Condensin I (blue rings) splits the big loops into smaller ones.
Chromosome loops (rainbow colors) wind around the helical scaffold (red rings), creating a tightly coiled bundle.
In around 15 minutes, cells can package roughly six feet of DNA into the tiny, condensed packages (right column) needed for cell division.