Spermatogenesis in Bombyx mori. II. The ultrastructure of synapsed bivalents.

J Morphol

Department of Biological Sciences, Northwestern University, Evanston, Illinois 60201.

Published: June 1971

AI Article Synopsis

  • In Bombyx mori, males are homogametic, and crossing over occurs solely in males with chiasmata found in spermatocytes, but not in oocytes.
  • The study identifies synaptonemal complexes in spermatocytes of young four instar larvae, indicating their role in genetic crossing over.
  • Using high-resolution electron microscopy, researchers describe the structure of meiotic bivalents and propose a three-dimensional model of synaptonemal complexes, detailing their origin and function during crossing over.

Article Abstract

In Bombyx mori the male is the homogametic sex, crossing over occurs only in males, and chiasmata are observed in spermatocytes, but not in oocyte nuclei. If the assembly of synaptonemal complexes is an essential prerequisite for genetic crossing over and chiasmata formation, then the nuclei of Bombyx spermatocytes should contain synaptonemal complexes. Synaptonemal complexes were found in spermatocytes from young four instar larvae. The structure of meiotic bivalents is described using micrographs taken with 100 and 1000 KV electron microscopes. These data together with that from the literature are used to construct a three-dimensional model of the synaptonemal complex and to suggest its method of origin and its function during crossing over.

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Source
http://dx.doi.org/10.1002/jmor.1051340204DOI Listing

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