PMID: 6161704Dec 1, 1980Paper

Structural paradox of polytene chromosomes

Cell
C D Laird

Abstract

The observation of thick chromatin fibers in interbands of Dipteran polytene chromosomes suggests that there should be 5 to 10 times more mass and DNA in interbands than is commonly thought to be present. To resolve this paradox, the chromatin content of interbands was estimated, using whole-mounted polytene chromosomes from Drosophila melanogster. Densitometry of high voltage electron microscopic negatives provides an estimate of less than 4:1 for the average ratio of cross-sectional dry mass (or mass per unit chromosome length) of bands relative to interbands. This ratio, combined with an estimate of the length of chromosome composed of interbands, indicates that at least 26% of chromosome mass is contributed by interband chromatin. Since DNA comprises a similar proportion of chromatin mass in bands and interbands (Laird et al., 1980b), these data imply that DNA sequences in interbands represent at least 26% of the euchromatic genome of D. melanogaster. This result calls for reinterpretation of some of the genetic and molecular data from Diptera. The discrepancy between this higher estimate of interband mass and DNA, and previous estimates of 3-5%, is discussed. One possibility is that previous measurements were made on promi...Continue Reading

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Citations

Aug 16, 2008·Chromosome Research : an International Journal on the Molecular, Supramolecular and Evolutionary Aspects of Chromosome Biology·E N AndreyevaI F Zhimulev
Aug 1, 1985·Proceedings of the National Academy of Sciences of the United States of America·A KrummG Korge
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Nov 24, 2017·Cold Spring Harbor Symposia on Quantitative Biology·Allan C Spradling
May 7, 2004·Development·Sarah B PierceRobert N Eisenman
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