title: Electron microscopic studies on the polytene chromosomes of Chironomus thummi salivary glands. I. Ultrastructural mapping.
abstract: The method of ultrathin sections of unsquashed salivary gland polytene chromosomes of Ch. thummi was applied to their ultrastrual mapping. There was a good agreement between electron micrographs and Hägele's light microscopic map (1970) with respect to the pattern and number of bands. 94% of bands were identified in larval and prepupal chromosomes. In Ch. thummi, band thickness varied from 0.05-0.5 mum. Most characteristic were 0.2-0.3 mum bands. Morphologically, bands were classified as: continuous (frequently with holes and gaps), discrete, dotted and continuous-discrete, discrete-dotted. Band morphology is related to band size, such that smaller bands, as a rule, were also dotted. Bands beginning to puff likewise became dotted. Interbands in unsquashed chromosome sections were from 0.05-0.15 mum. The smallest interbands contained only fibrils, in the larger interbands few granules could be observed. This makes interbands distinguishable from a typical puff with many such granules.
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D002875:Chromosomes / Q000648:ultrastructure*; D004175:Diptera / Q000166:cytology*; D008854:Microscopy, Electron; D012469:Salivary Glands / Q000648:ultrastructure*