Meiotic stages

FIG. 2. Scheme of mammalian spermatogenesis showing the premeiolic and meiotic stages of spermatogenesis and postmeioiic spermiogenesis with the development and maturation of the spermatozoa. 

Parker, D. R. (1968), A survey of methods for the induction of aberrations in meiotic stages in Drosophila females and for observation of their disjunctional properties in the ensuing meiotic divisions, in "Effects of Radiation on Meiotic Systems, International Atomic Energy, Vienna, 209-218. 

Wassarman, P. M., Josefowicz, W. J., and Letoumeau, G. E. (1976). Meiotic maturation of mouse oocytes in vitro inhibition of maturation at specific stages of nuclear progression. J. Cell Sci. 22 531-545. 

After the DNA is replicated during prophase of the first meiotic division, the resulting sister chromatids remain associated at their centromeres. At this stage, each set of four homologous chromosomes exists as two pairs of chromatids. Genetic information is now exchanged between the closely associated homologous chromatids... 

Upper Left A pair of mitotic sister chromatids in a section stained with an antibody to topoisomerase II. Notice that the two chromatids are coiled with opposite helical handedness. Lower Left Meiotic chromosomes of a lily at the pachytene stage in which sister chromatids are connected along their length in a synaptonemal complex. From Kleckner, N. (1996) Proc. Natl. Acad, Sci U.S.A. 93, 8167-8174... 

During the prophase of the first meiotic division (meiosis I) two homologous pairs of partially "condensed" chromosomes must find each other and pair with appropriate orientation. A protein in the telomeres of the chromosomes seems to be involved.269 277 The key structure in meiotic crossing-over is the ribbonlike synaptonemal complex formed by the pairs of homologous chroma fids.271/278 2791 This complex, in which a proteinaceous core or axial element separates the greatly extended chromatid pairs (Fig. 26-13), is fully formed in the pachytene stage of meiosis. Formation of the synaptonemal complex is preceded by development of a few double-stranded breaks in... 

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