| Nuclear division and chromosome cycle in microsporidia. | |
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MedLine Citation:
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PMID: 3134965 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Nuclear division and chromosome cycle of microsporidia are reviewed in the light of recent speculation that the group diverged as an early branch in the eukaryotic line of descent. Microsporidia are primitive eukaryotes with simple cytoplasmic organisation, lacking mitochondria, peroxisomes and a classical Golgi apparatus. The ribosomes resemble prokaryotic ribosomes in size and in having sequences complementary to the eukaryotic 5.8S rRNA contained within their large (23S) ribosomal subunit, rather than a separate 5.8S molecule. Nuclei may be isolated or closely appressed as a diplokaryotic pair which divide synchronously. Mitosis is intranuclear: there are no centrioles but spindle termini are electron dense plaques in pores in the nuclear envelope. Some genera have isolated nuclei throughout the life cycle, while others have diplokaryotic nuclei throughout: meiosis is not known in either of these categories of genera. In contrast, certain polymorphic species, which are transmitted horizontally between copepods and mosquitoes and vertically between generations of mosquitoes, alternate between stages with isolated nuclei and stages with diplokaryotic nuclei. Haploid spores in copepods are infective to mosquito larvae, in which gametogenesis and plasmogamy occur to give diplokaryotic (diploid) stages. Stages remain diplokaryotic through transovarial transmission to the next generation, when an unusual form of meiosis is initiated in both nuclei of the diplokaryon (as indicated by synaptonemal complexes), and mingling of chromosomes occurs when the two nuclei fuse during pachytene. |
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Authors:
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E U Canning |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Bio Systems Volume: 21 ISSN: 0303-2647 ISO Abbreviation: BioSystems Publication Date: 1988 |
Date Detail:
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Created Date: 1988-09-01 Completed Date: 1988-09-01 Revised Date: 2003-11-14 |
Medline Journal Info:
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Nlm Unique ID: 0430773 Medline TA: Biosystems Country: NETHERLANDS |
Other Details:
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Languages: eng Pagination: 333-40 Citation Subset: IM |
Affiliation:
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Department of Biology, Imperial College of Science and Technology, London, U.K. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Apicomplexa / cytology*, ultrastructure Cell Cycle* Cell Division* Cell Nucleus / ultrastructure* Chromosomes / ultrastructure* Microscopy, Electron Phylogeny |
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