The human chromosome. Electron microscopic observations on chromatin fiber organization.
Human lymphocytes were grown in short-term tissue culture and were arrested in metaphase with Colcemid. Their chromosomes were prepared by the Langmuir trough-critical point drying technique and were examined under the electron microscope. In addition, some chromosomes were digested with trypsin, Pronase, or DNase. The chromosomes consist entirely of tightly packed, 240 +/- 50-A chromatin fibers. Trypsin and Pronase treatments induce relaxation of fiber packing and reveal certain underlying fiber arrangements. Furthermore, trypsin treatment demonstrates that the chromatin fiber has a 25-50 A trypsin-resistant core surrounded by a trypsin-sensitive sheath. DNase digestion suggests that this core contains DNA.
D000328:Adult; D002842:Chromatids; D002874:Chromosome Mapping; D002906:Chromosomes, Human, 6-12 and X; D046508:Culture Techniques; D003582:Cytogenetics; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000166:cytology*; D008854:Microscopy, Electron