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AN ULTRASTRUCTURAL EXAMINATION OF CHROMOSOME PAIRING DURING MEIOSIS (TRADESCANTIA)

Whole mount spread preparations of Tradescantia nuclei were used to examine synaptonemal complex (SC) formation. Tradescantia spreads have the standard SC morphology. Kinetochores and recombination nodules were not regularly observed. Thickenings of the lateral elements were observed and increased in numbers between mid- and late-zygotene. The thickenings were distributed evenly amongst the chromosomes, but were nonrandomly distributed within a chromosome. They were underrepresented in unsynapsed regions and overrepresented in synapsed regions, especially in synapsed regions near the junction with an unsynapsed region. / Lateral component material is well formed along the chromosome axis before SC formation begins. In early- and mid-zygotene the telomeres occur in a restricted region and have modifications for attachment at or near the nuclear envelope. Initiation of SC occurred at many sites along the chromosomes; regions nearer the telomeres had a greater tendency to form SC first. Between 29 and 106 initiation sites were observed in the early-zygotene nuclei. The average distance between initiations ranged from 7.3 to 11.2 (mu)m. The total number of potential initiation sites was estimated and ranged from 250-299. / Foldback synapsis was observed in all nuclei of Clone 02. The extent of the foldback synapsis was fairly constant at all stages examined. / The results from Tradescantia and other organisms was considered, and a model of SC formation was proposed. The key aspect of the model is that SC formation does not require homology. Synthesis of zygotene DNA is required for SC formation and is regulated such that homologous regions are in close proximity as their zygotene DNA is synthesized. This proximity, just as homologous regions have been made competent to form SC, makes it highly likely that homologous SC formation will ensue. / Source: Dissertation Abstracts International, Volume: 45-01, Section: B, page: 0061. / Thesis (Ph.D.)--The Florida State University, 1984.

Identiferoai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75268
ContributorsHASENKAMPF, CLARE A., Florida State University
Source SetsFlorida State University
Detected LanguageEnglish
TypeText
Format166 p.
RightsOn campus use only.
RelationDissertation Abstracts International

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