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Genetics Lecture No. 24.docx

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Western University
Biology 2581B
Jim Karagiannis

Genetics Lecture No. 24: Susanne Kohalmi’s Favourite Things th Monday April 8 , 2013 Marine Slugs & Chloroplastic Genome: -Elysia chlorotica is a marine slug that captures chloroplasts through its heavy diet of the Vaucheria alga. These symbiotic chloroplasts are actually translationally active and functional genes from ingested chloroplasts have been transferred to the slug’s nuclear genome. The symbiotic chloroplasts residing in the host molluscan cell are maintained by an interaction of both organellar and host biochemistry directed by the presence of transferred genes. Trypanosomes: -Trypanosomes are group of unicellular parasitic flagellate protozoa that often require transmission via a vector in order to live in mammals, insects, etc. They live in more than one host species over their life cycle are often transferred from the saliva glands of carrier insects such as mosquitos into the bloodstream of mammals. Trypanosomes are important as they represent a natural mechanism of transferring genetic material between organisms. These parasites have very interesting mitochondrial genomes that are very dense and shaped like hockey pucks. These genomes contain hundreds upon hundreds of interconnected rings known as minicircles. In trypanosome mitochondria, genomes follow a chainmail model where there is a valency of 3 rings connected to a central ring. However the valency can change during replication when 6 rings become connected to the central ring. This process does not increase the size of the physical size of the “hockey-puck” genome since the rings are packed more densely. Tetrahymena: -Tetrahymena is a eukaryotic protist with two nuclei: A diploid germline nucleus that remains transcriptionally silent throughout asexual reproduction and a somatic nucleus that is transcriptionally active. The somatic nucleus is received from both parents, but eventually gets deleted before the cell forms its own new sexual identity, of which there are 7 different sexes to choose from! Tetrahymena can mate with any mating type other than their own and they do this through programmed genome rearrangement. In the germline genome of Tetrahymena are 7 copies of different genes in a duplication pair that are incomplete (missing parts). In the somatic genome, these genes will recombine with each other in order to form completed duplication pairs which will define the sex type. This outcome is completely unpredictable, the result of a game of “genetic roulette.” Green Fluoresce
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