Identifiable regions of Drosophila melanogaster polytene chromosomes visualized by whole mount electron microscopy

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Electron microscopic analysis of the divisions 1 and 2 in the salivary gland chromosome X of Drosophila melanogaster reveals at least 100 recognizable bands. This number is ca. 75 % higher than the respective number of those bands drawn by Bridges (1935) in his original light microscopic reference map, ca. 15 % higher than given by Bridges (1938) in his revised map of the X chromosome, and ca. 78 % higher than revealed by earlier electron microscopic analyses of the same divisions. The main difficulty in comparison of results with Bridges' maps has been the definition of real structural double bands. According to our interpretation only about 80 % of Bridges' doublets in division 1 and 2 are double structures also in the electron micrographs. Possible reasons for the high number of double bands in Bridges' maps and, on the contrary, for too low number of bands revealed by some earlier EM studies are discussed.

“…More resemblance with normal light microscopic view can be obtained in the electron microscopy of spread salivary gland chromosomes (cf. ALANEN and SORSA 1978).…”

Section: Observations and Discussionmentioning

confidence: 99%

Electron microscopic analysis of the banding pattern in the salivary gland chromosomes of Drosophila melanogaster. Division 1 and 2 of X

Sorsa

Saura

2009

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“…The project for the localization of the heat shock band in division 81 of Drosophila hydei polytene chromosomes was initiated in order to find out whether whole mount electron microscopy (ALANEN and SORSA 1978) could be used for mapping of active genes. The heat shock puff in division 81 waschosen because it was known to originate from an area of very thin bands and was thus presumed to test critically the limits of the method's resolution.…”

Section: Discussionmentioning

confidence: 99%

“…The situation is, however, rapidly changing as the electron microscopic maps of D. melanogaster are being compiled (e.g., SoRsAet al 1984). The development of rapid EM whole mount methods capable of preserving the light microscopic structure of polytene chromosomes (ALANEN and SORSA 1978;ALANEN 1981;KALISCH 1982) has made it possible to apply electron microscopy for routine studies of polytene chromosomes.…”

mentioning

confidence: 99%

Identification of a heat shock locus by whole mount electron microscopy of polytene chromosomes

Alanen

2008

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The suitability of whole mount electron microscopy for the localization of gene activity in polytene chromosomes was tested by heat shock induction in Drosophila hydei. The heat shock response of salivary glands is found out to be detrimental to surface spreading properties of salivary gland material. The major heat shock band in division 81 is determined to be 81C2. The heat shock puff is covered by amorphous material probably representing transcription complexes that partly obscure the underlying structures. After 5 min heat shock treatment, spherical particles are observed on the puff site. Successful mapping of this region, which consists of very thin bands including a developmental puff, suggests that whole mount electron microscopy is the method of choice for routine localization of gene activity in polytene chromosome systems.

“…Ten years later BURKHOLDER (1976) introduced an elegant method for the preparation of whole mount spreads from the salivary gland polytene chromosomes. It was soon ascertained that the method is suitable for electron microscopic mapping of Drosophila melanogaster polytene chromosomes (ALANEN and SORSA 1978). Since then several attempts at whole mounting polytene chromosomes have been reported (e.g., hut these methods have not been taken into general use by the researchers concerned with the mapping of polytene chromosomes.…”

mentioning

confidence: 99%

Whole mount electron microscopic maps of Drosophila melanogaster polytene chromosomes

Alanen

2008

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Whole mount electron microscopic maps of Received March 11, 1985A simple whole mount method has been used for electron microscopic observation of the polytene chromosomes from the salivary glands of Drosophila melanogasfer. The method makes it possible to observe polytene chromosome arms, that are suitable for mapping often along their entire length. A map to facilitate easy localization of bands in the chromosome X together with examples of whole mount spreads prepared by the method are presented.