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Identifier uch.biology.msc//1998ladoukakis
Title Φυλογεωγραφική μελέτη του μυδιού της Μεσογείου Mytilus galloprovincialis σε σχέση με τη διπλή μονογονική κληρονομικότητα του μιτοχονδριακού DNA.
Author Λαδουκάκης, Εμμανουήλ
Thesis advisor Ζούρος, Ελευθέριος
Abstract Mitochondrial DNA (mtDNA) has been extensively used for phylogenetic and population studies in animals. Interpretation of results relies on maternal inheritance of mitochondrial genomes. Mussels of the genus Mytilus show a different type of mtDNA transmission, which has been called Doubly Uniparental Inheritance (DUI). According to this mechanism, females are homoplasmic for a type of mtDNA, called type F, which they transmit to both daughters and sons. However, males are heteroplasmic for an F type and another type which appears exclusively in males (the M type). Males transmit exclusively the M type to sons, but not to daughters. The double transmission system and the lack of recombination of mitochondrial genomes imply the existence of two different lineages of mtDNA: the F and the M. Males have been observed that do not have an M type, producing sperm that contains the F type only. This provides the opportunity for the emergence of a new M lineage that is closer, in terms of sequence, to the F type genomes. This phenomenon has been termed «masculinization» of the F lineage, and will produce males heteroplasmic for types belonging to the F lineage. We have used this system to study the phylogeography of the Mediterranean mussel Mytilus galloprovincialis. Samples from the Black Sea, the Eastern Mediterranean and the Atlantic coasts of Europe were scored for variation at the mitochondrial COIII and 16S rDNA genes by using a PCR-RFLP method and a total of 5 different restriction enzymes. The results indicate that all the females (except of 2) are homoplasmic and most of the males are heteroplasmic. As expected, F and M haplotypes group separately in phylogenetic analysis. In the Mediterranean and Atlantic samples, an overwhelming majority of males are heteroplasmic for an F and an M type. However the majority of the Black Sea males are heteroplasmic for two types that belong to the F lineage, indicating the spread of M types hat resulted from masculinization events some time ago. In addition, some males from the Black Sea and Mediterranean populations appeared as homoplasmic for an F type. These could be truly homoplasmic, or reflect the existence of a masculinized F type that has diverged little from the F type from which it sprang. These results show the great importance of masculinization in interpreting the phylogeography of Mytilus species, and possibly other bivalves.
Language Greek
Issue date 1998-11-19
Date available 1998-10-07
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
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