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Lecture 98

BIOL 3600 Lecture Notes - Lecture 98: Alphaproteobacteria, Archezoa, Nuclear MembranePremium

6 pages59 viewsWinter 2017

Department
Biology
Course Code
BIOL 3600
Professor
Spencer
Lecture
98

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Origin of Complex Life: Eukaryogenesis
20 April 2017
G. Ozan Bozdag
Why are we focusing on the evolution of complex cell?
o Microbial life starts 3.7 bya, with bacteria and archaea
o Can evolve to become multicellular but not complex
Eukaryotic cell(s): Cell within a cell
o Mitochondria can reproduce independent of the cell
They have their own genomes
o Eukaryotic cell is very different from prokaryotic cell
Evolution of eukaryotes: Not a regular evolutionary change
Cells within cells: Modern examples of phagocytosis
o Endosymbionts inside larger cells which can reproduce
Edosyioti Hypothesis Theory
o 1905: Mereschkowski thought larger cells engulf smaller cells
o 1967: Margulis reintroduced Mereshkoskis idea after people
forgot about it; extrapolated to animal cells, not just plant cells
EukaryogenesisA major transition in evolution
o Not a simple branching into 2 from 1 lineage
o 1+1=1
o Over 15 hypothesis for the origin of the host
o 17 different hypothesis for origin of the endosymbiont
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Part 1: Origin of the mitochondria
o Mitochondria form a clade
o They share similar genomes with alpha-proteobacteria
o The endosymbiont was an alpha-proteobacteria
o Genome reduction in organelles
When alpha-proteobacteria entered cell, caused huge
genome reduction
o Genome reduction in mitochondria
Protist mtDNA share some genes with yeast mtDNA, but
they share with alpha-proteobacteria
o How does the transfer happen: RNA-intermediate or bulk-
transfers?
o Origin of the mitochondrion (the organelle): Not that simple!
Not all of the 1,100 proteins come from alpha-
proteobacteria to mitochondria
o  Ogoig deate
Alpha-proteobacteria form with premitochondrion to form
mitochondria
Part II: Origin of the host
o Nuclear genome is more identical to the archaeal lineages
o Other than self-replicating organelles: Intracellular
membranes/trafficking
Carries nutrients to cell; waste away from cell
Composed of different extensions of membranes, different
proteins
Not found in bacteria
o 2 competing hypotheses
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