Electron microscope analysis of the E polytene chromosome of Drosophila subobscura: region 70B to 72D

Abstract

Revision of the reference map of the polytene chromosomes of Drosophila subobscura was started by means of the electron microscope. We present a map of regions 70B to 72D of the E chromosome obtained from squashed and thin-sectioned salivary glands. It was observed that the total number of bands in divisions 70B to 72D is considerably higher than those depicted in the reference map of Kunze-Mühl and Müller. Functional considerations are made of some regions that show puff structures.

Ultrastructure of E1 + 2 + 9 + 12 inversion breakpoints in Drosophila subobscura

“…These differences are in general larger than those described by Sorsa's and Zhimulev's groups [21,25,26,29,34,36,39] for Drosophila melanogaster with respect to Bridges' map. In addition, larger differences have been found compared with other regions previously analyzed in Drosophila subobscura [5,20]. The map of Kunze-Mfihl and M~iller [17] for Drosophila subobscura is not as precise as Bridges' for Drosophila rnelanogaster.…”

“…The use of electron microscopical techniques [3,12,19,33] has allowed detailed insight into the structural organization of polytene chromosomes. Several technical improvements have been carried out, for instance: a) to study the banding patterns and construct chromosome maps [4,5,13,14,20,22,23,[35][36][37]39] ; b) to investigate the informational content of precise sections related to transcriptional activity [2,[24][25][26]30] ; c) the ultrastructure of the insertion sites of mobile elements in the polytene chromosomes [27,28], as well as the formation and transpors of RNA-protein complexes [1,6,11,31,38].…”