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Identifier uch.biology.msc//2002theologidis
Title Οι επιπτώσεις του ανασυνδυασμού του μιτοχονδριακού DNA στη δυναμική του συστήματος της διπλής μονογονικής κληρονόμησης (DUI) του mtDNA του μυδιού mytilus galloprovincialis
Thesis advisor Θεολογίδης, Ιωάννης
Thesis advisor Ζούρος, Ελευθέριος
Abstract The bivalves of family Mytilidae show an unusual pattern of mtDNA inheritance. Female individuals inherit an mtDNA type that derives from their mother. Male individuals, however, inherit also their father's mtDNA (M type). Therefore, two evolutionary lineages of mtDNA coexist in the same species: the one that is transmitted through the eggs (F lineage) and the one that is transmitted through sperm (M lineage). This system of mtDNA transmission has become known as Doubly Uniparental Inheritance (DUI). The present thesis focused in two separate aspects of DUI. The first concerned the recent evidence that mtDNA molecules in male gonads undergo homologous recombination. The second is related to the phenomenon of “masculinization”. In certain cases, F type molecules enter the male lineage displacing M type molecules and setting the differentiation time of the two lineages to zero. This phenomenon is described by the term “masculinization” and the masculinized molecules are symbolized as MF. The present thesis had two separate aims: A) The recent discovery of recombination raised the question whether the recombinant mtDNA molecules are transmitted in the next generations and they pass on natural populations. We examined separately the case of maternally transmitted molecules and the case of paternally transmitted molecules. With respect to the first case, we were focused in a female individual, which appeared to carry a recombinant mtDNA molecule, according to a previous restriction analysis of its COIII gene. The analysis of the recovered sequence of this gene revealed that this molecule was not recombinant, but instead typical F type molecule with specific mutations at some restriction sites that made it resemble an M type molecule. Relatively to the second case, we examined all the male individuals of a previous study, which had characterized these individuals according to the restriction patterns of two segments of their mtDNA molecules. We added a new segment that corresponded to a fragment of 900bp of the COI gene. According to the results, it appears that recombinant molecules of paternal origin do exist and they are transmitted to the next generations, as well. B) Until the discovery of recombination, the study of a segment was enough in order to characterize a molecule as masculinized. The discovery of recombination imposed the review of the phenomenon of masculinization, with the rationale that the diagnostic segment that characterized a molecule could be a result of recombination. An important number of paternal molecules, which carried F type sequences at least in three distinguishable segments, were found. The probability that such molecules could result from multiple recombination events and that these recombinant molecules were fixed in the population is very small. This observation is compatible with the existence of masculinization. Conclusively: · Recombinant molecules of maternal origin do not exist in populations. · Powerful evidence is provided that recombinant molecules of paternal origin do exist and do pass on natural populations. · The phenomenon of masculinization does occur.
Language Greek
Issue date 2002-11-22
Date available 2002-10-09
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
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