Meiosis in drosophila melanogaster 1. chromosome identification and kinetochore micro tubule numbers during the 1st and 2nd meiotic divisions in males

Lin, H.P.P.; Ault, J.G.; Church, K.

Chromosoma 83(4): 507-522


ISSN/ISBN: 0009-5915
Accession: 005873821

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Individual bivalents or chromosomes were identified in D. melanogaster spermatocytes at metaphase I, anaphase I, metaphase II and anaphase II in EM of serial sections. Identification was based on a combination of chromosome volume analysis, bivalent topology and kinetochore position. Kinetochore microtubule numbers were obtained for the identified chromosomes at all 4 meiotic stages. Average numbers in D. melanogaster are relatively low compared to reported numbers of other higher eukaryotes. There are no differences in kinetochore microtubule numbers within a stage despite a large (approximately 10-fold) difference in chromosome volume between the largest and the smallest chromosome. A comparison between the 2 meiotic metaphases (metaphase I and metaphase II) reveals that metaphase I kinetochores possess twice as many microtubules as metaphase II kinetochores. Other microtubules in addition to those that end on or penetrate the kinetochore are found in the vicinity of the kinetochore. These microtubules penetrate the chromosome rather than the kinetochore proper and are more numerous at metaphase I than at the other division stages.