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Meiosis in a living crane fly spermatocyte [Meiosis II]
Author
La Fountain Jr., James
Oldenbourg, Rudolf
Abstract
Presents the events of meiosis II in two living spermatocytes obtained from the testis of a crane-fly larva are viewed in polarized light and recorded in this time-lapse sequence beginning at prophase II through telophase II to the near completion of cytokinesis following meiosis II.
Noteworthy features of meiosis in crane-fly spermatocytes:
a) The duration between nuclear envelope breakdown (NEB) and the onset of anaphase II lasts on average about 45 minutes.
b) Upon NEB, birefringent microtubules are assembled from the two polar centrosomes, and some of these attach to the kinetochores of dyad chromosomes.
c) Kinetochore fibers appear distinct due to their birefringence, which is readily detected with polarized light microscopy.
d) At metaphase, the spindle has a characteristic bi-cone shape, and its kinetochore fibers have striking bright birefringent contrast.
e) Anaphase A (kinetochore fibers shorten) is followed by anaphase B (spindle elongation) resulting in segregation of haploid chromosome sets to opposite poles of the cells.
f) Within a few hours of the completion of cytokinesis, the resultant spermatids begin to elongate as they begin the process of spermiogenesis that will result over the course of several days in formation of mature haploid spermatozoa Componente Curricular::Educação Superior::Ciências Biológicas::Biologia Geral