Letter from Francis Crick to Aaron Klug DNA Chromatids Crick expressed reservations about the evidence used by his two co-authors in support of their idea that chromatids, the one-half of a chromosome that splits off from the other half during cell division, were organized in a hierarchy of helices: the chromatid is a folded and coiled super-solenoid (a long, regular, hollow cylindrical structure), also called the unit fiber, which in turn is formed by a coiled solenoid of smaller diameter, which in turn is formed by coiling the string of nucleosomes, bead-like complexes of DNA and protein.. See Leth Bak, Jesper Zeuthen, and Crick, "Higher-Order Structure of Human Mitotic Chromosomes," Proceedings of the National Academy of Sciences, vol. 74 (April 1977), pp. 1595-99. Produced: 17 January 1977 The Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers Crick, Francis Letters (correspondence) Archival Materials Text 2 pages nlm:nlmuid-101584582X242-doc 101584582X242 http://resource.nlm.nih.gov/101584582X242 Profiles ID: SCBBQT English Profiles in Science