LE3 .A278 2010

2010

Stewart, Don

Acadia University

Bachelor of Science

Honours

Biology

Biology

Certain species of marine mussels, specifically those in the Mytilus genus, have been found to exhibit a unique system of mitochondrial DNA ( mtDNA) inheritance. Instead of the typical exclusive maternal mtDNA inheritance found in most animals, these mussels possess an alternative method of inheritance, involving paternal as well as maternal inheritance. Mytilus species have two distinct mitochondrial genomes, known as the F genome ( maternal) and the M genome ( paternal). These two genomes are inherited independently; therefore, the system of inheritance is known as doubly uniparental inheritance ( DUI). The Mytilus genome is 17kb long, it codes for 13 proteins and it has five unassigned regions, one of which is hypothesized to be the control region. The F and M genomes are highly divergent within a population; however, every once in a while the F genome can assume the role of the M genome and be passed through the paternal line. This is referred to as a masculinization event and it results in a recently masculinized ( RM) genome. During a masculinization event, recombination creates a “ chimeric” RM genome which has a duplicated control region of F and M origin. It has been suggested that this M control region ( or at least part of it) is homologous in all male Mytilidae mussels, that it plays a critical role in the mechanism behind the DUI system and that it may influence sex determination. The goal of this project was to amplify and sequence the control region in Modiolus modiolus ( a close relative of Mytilus spp.) and in RM Mytilus edulis to see if this hypothesis is supported. The approach for these two species was similar. For M. modiolus, universal primers for CytB and 16S were used to amplify these respective genes through polymerase chain reaction ( PCR). The PCR products were sent to the McGill University and Genome Quebec Innovation Center for sequencing and the resulting sequences were aligned. Sex- specific primers were developed for the CytB and 16S genes flanking the control region. These flanking primers were then applied to M. modiolus, along with other primer combinations, 2 to amplify the control region. For RM M. edulis, 16S forward and CytB reverse primers were available for PCR amplification. The PCR product was inserted into a plasmid vector, cloned and then sequenced. Using ClustalW Alignment, the resulting sequence was found to align closely with the control region of Mytilus species. Primers were created from the highly conserved regions of the RM sequence alignment and have been tested on the RM M. edulis males. The control region amplifications for both of these species produced visible bands of the appropriate size; however, sequencing results were relatively inconclusive, thus further amplification, cloning and sequencing must be done.

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https://scholar.acadiau.ca/islandora/object/theses:684