Crick here commented again on the draft of a paper by Klug on the spatial arrangement of DNA and histones (proteins associated with DNA) in nucleosomes, particularly on the dimensions of the DNA helix, whether the DNA helix was itself coiled in a nucleosome (forming a coiled coil, or superhelix), and the number of base pairs per turn of the superhelix. Crick also pointed out that as DNA shrank from its hydrated, elongated B form (or fiber form) to its shorter, drier A form, the X-ray diffraction patterns of DNA in nucleosomes changed in ways that might affect Klug's conclusions.
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