ELECTRON MICROGRAPH MAP OF THE DROSOPHILA-MELANOGASTER POLYTENE CHROMOSOME-3R DIVISION-91 THROUGH DIVISION-100

The banding pattern of the distal half of the polytene salivary gland 3R chromosome of Drosophila melanogaster was studied by means of the t hin section electron microscopy. Bands were identified according to th e revised light microscopic map of Bridges. Bridges' map contains 332 single bands and 137 double bands within the region 91 through 100. Th is makes a total of 606 bands when the doublers are counted as two ban ds each, but 469 bands when the doublers are counted as one band. In t he electron micrographs we found a total of 443 bands within this regi on. 109 Bridges' singlets were easily detected in almost all thin sect ions, while 144 mainly faint bands could be seen only in some microgra phs. 79 Bridges' single bands and one doublet (94D7-8) could not be fo und. 42 Bridges' doublets were made up of two separate bands each, 87 Bridges' doublers looked single, and three pairs of Bridges' doublers formed dark complexes in the thin sections. The telomere region with t he most distal band 100F4-5 was gray. A total of 15 new bands, which a re not drawn on Bridges' map, were detected. Most of the new bands wer e in the divisions 96 and 99.