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Lecture 10

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Biology 1002B
Denis Maxwell

Lecture 10: Evolution of Eukaryotes 1. Meaning of endosymbiosis and lateral gene transfer  Endosymbiosis o Mitochondria, chloroplasts may originate from symbiotic relationships between two prokaryotes  Lateral gene transfer o Genes from mitochondrion or chloroplast relocated to the nucleus over millions of years o Nucleus can take control o Only thing that changed is the relocation of the gene but not what the gene does 2. Origin of endomembrane system, nuclear membrane, ER etc.  Endomembrane – series of intracellular membrane compartments found in eukaryotic cells  Membranes are similar in fatty acid and structures  Endomembrane defining characteristic of eukaryotes o nuclear envelope derived from infolding of plasma membrane o ER connected to nuclear envelope o ER and nuclear envelope is very distinct from endomembrane system and endosymbiosis  (Endomembrane system) Ancestral bacterium  infolding of plasma membrane  nuclear envelope and ER  (endosymbiosis) aerobic bacterium  cyanobacterium  Having a nucleus means you can control transcription and translation (advantageous) o Bacteria cannot do this because everything is in the same compartment  Early cell may be anaerobic o Small aerobic bacteria advantage with more ATP 3. Origin of mitochondria and chloroplasts  Mitochondria and chloroplast derived from free living prokaryotic cells (endosymbiosis) o Not derived from the same place as the nucleus  Mitochondria derived from aerobic bacterium  Aerobic ancestral bacteria advantage through phagocytosis to bring aerobic bacteria to provide ATP  Chloroplast derived from cyanbacterium 2 mya o Identical photosynthetic structure  Most eukaryotes have mitochondria o Endosymbiosis of aerobic bacterium predated uptake of cyanobacteria  Split into animals and plants (cyanobacterium branch)  Aerobic bacterium got taken up first 4. Evidence supporting theory of endosymbiosis  Endosymbiosis between cyanobacterium, aerobic bacterium and host o Only group of bacteria that go through oxygenic photosynthesis o Cyanobacterium became modern chloroplasts  Identical morphology between mitochondria and bacteria  Formation and division – no genes that code for chloroplast, mitochondria  Electron transport chains o Descended from free living bacteria that can make ATP and support themselves  Genome o Have their own genome, transcription/translation machinery 5. Factors driving development of early eukaryotic cells  Oxygen o Earliest bacteria was anaerobic that got ATP through glycolysis and fermentation o 2.2 bya, cyanobacteria  Oxygenic photosynthesis t
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