Replication in Drosophila chromosomes

Lakhotia, S. C. ; Sinha, P. (1983) Replication in Drosophila chromosomes Chromosoma, 88 (4). pp. 265-276. ISSN 0009-5915

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DNA fibre autoradiography of highly polytenized nuclei in salivary glands of Drosophila nasuta larvae reveals two distinct types of active replicons. Type I replicons are longer (mean size=64 μm), have a very high rate of fork migration (average rate=0.95 μm/min) and generally occur in large arrays often extending over several thousand μm. In contrast, the type II replicons are smaller (mean size= 20 μm), slow replicating (average rate=0.07 μm/min) and occur in short arrays containing only a few closely spaced active replicons. Evidence is presented that type I replicons are active in the early S and type II in the late S. Observations on autoradiographic labelling of partially lysed polytene chromosomes provide evidence for a lack of temporal and spatial agreement in the activation of origin points in homologous regions of the lateral polytene strands; these observations also suggest local variations in levels of polyteny within a chromosome. On the basis of this and other available information on replication in polytene chromosomes the possible roles of the two replicon types in the generation of the different 3H-thymidine labelling patterns of polytene chromosomes are discussed.

Item Type:Article
Source:Copyright of this article belongs to Springer-Verlag.
ID Code:22049
Deposited On:23 Nov 2010 08:38
Last Modified:06 Jun 2011 08:39

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