Abstract
SINCE the discovery of giant salivary gland chromosomes in dipterous larvæ1, cytophysiologists have regarded them as the most favourable material for studying the chemical composition and fine structure of chromosomes, especially the leptonic relation between nucleic acid and protein. The view that chromosomes are chiefly composed of nucleoprotein is now generally accepted. In salivary gland chromosomes, the bands represent regions of relatively high nucleic acid content, while the interbands carry very little, if any, nucleic acid. The results obtained by Feulgen staining2, histochemical tests3 and ultraviolet microscopy4 have all substantiated this conclusion. Digestion experiments by Caspersson and by Mazia and Jaeger5 clearly indicate that the salivary gland chromosomes possess a continuous protein framework the integrity of which is independent of the presence of nucleic acid molecules. In a more definite way, Astbury and Bell6 and Schmidt7 concluded from their X-ray diffraction and birefringence data that the most important elements in the molecular organization of the chromosomes are the partially folded and partially extended polypeptide chains, together with the parallel fitting of thy-monucleic acid on to the extended portion of the chains. Based on this structural principle, Pfeiffer8 and especially Calvin and Kodani9 have proposed a probable structure for the salivary gland chromosome.
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CHU, J., PAI, S. Constitution of the Salivary Gland Chromosomes of Chironomus. Nature 155, 482 (1945). https://doi.org/10.1038/155482a0
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DOI: https://doi.org/10.1038/155482a0
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