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Meiosis plays an integral role in the evolution of
eukaryotes and recA homologs are key genes involved in this biological
process. RAD51 is the gene responsible for recombination processes
in general whereas DMC1 is involved only in meiosis. Both of these
genes have been identified in numerous eukaryotic organisms some
having only the RAD51 gene and some with both genes. However surprisingly
the diplomonad Giardia lamblia has two copies of the DMC1 gene while
apparently lacking the RAD51 gene entirely. This research project
aims to examine G. lamblia’s closest relatives including other
diplomonads and some retortamonads. Our study was designed to see
if these species are also missing the RAD51 gene and/or have two
DMC1 orthologs. This information will help to discover the evolutionary
history of these genes including the point at which the DMC1 gene
duplicated and when the RAD51 gene was apparently lost. We examined
four species: Trepomonas agilis Hexamita inflata Spironucleus barkhanus
and Retortamonas sp. Using degenerate and nested PCR with multiple
primer combinations nearly 200 gene candidates were cloned and sequenced.
Thus far we have been unable to find RAD51 or DMC1 genes in these
species. In addition we have carried out an updated phylogenetic
analysis of recA homologs in all eukaryotes focusing on protists.
Database mining and alignment of recA sequences were used to construct
phylogenetic trees which are discussed herein.
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