Abstract
IN discussing the relation of the nucleolus with the SAT chromosomes, investigators do not appear to notice that the ‘constriction’ is probably due to the nucleolus, rather than an active producer of that body1. I imagine the chromosome in a close spiral. The nucleolus develops at a definite point in the chromosome and pushes the spirals apart until that part of the chromosome becomes a straight thread and apparently much thinner than the remainder of the chromosome. When the SAT chromosome in Navashin's Crepis2 was not able to develop a nucleolus because the nucleolar material had already been removed by another chromosome, it had no satellite either. The darkly staining portions just below the thin stalk in McClintock's Zea chromosomes3 could also be explained by the spirals beyond the nucleolus being pushed more closely together.
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References
Gates, R. R., NATURE, 141, 794, (1939).
Navashin, Cytol., 169 (1934).
McClintock, B., Zeit. Zell. und Mikr. Anat., 21, 294, (1934).
Metz, C. W., and Poulson, D. F., J. Morph., 63. No. 2, 363 (1938).
Melland, A. M., unpublished.
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MELLAND, A. Relation of the Nucleolus to Secondary Constrictions. Nature 144, 980 (1939). https://doi.org/10.1038/144980b0
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DOI: https://doi.org/10.1038/144980b0
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