• Endosymbiotic Theory: Mitochondria & Chloroplast are descendants of prokaryotic cells; they share clear structural/ biochemical features with modern prokaryotes.
  • Cyanobacteria: blue-green algae; obtain their energy through photosynthesis
  • Lateral gene Transfer: Gene from Mitochondria & Chloroplast MOVE from Mitochondria & Chloroplast to the nucleus

Evidence of Endosymbiosis (Happened after evolution of aerobic prokaryotes)

  • Morphology: Form of both Mitochondria/ Chloroplast is similar to that of a prokaryotic cell
  • Reproduction: cell cannot make a Mitochondria/ Chloroplast. They arise from preexisting ones via Binary Fission.
  • Genetic Info: They have their own DNA; some have been moved by lateral gene transfer
  • Transcription/ Translation: Both Mitochondria/ Chloroplast contain full transcription/ translation machinery
  • Electron Transport: Mitochondria/ Chloroplast generate energy through ETC
Endosymbiosis: Evidence & Evolution

What Drove Early Eukaryotic Cells?

  • The arise of oxygenic photosynthesis via cyanobacteria gave rise to an extreme advantage (eukaryotes (increase size due to increase ATP production)
  • Ex: Rubisco Assembly– LSU genes found in Chloroplast and SSU genes found in Nucleus; must coordinate for expression

Case Study: Giardia

  • Giardia (Diplomonad) single cell eukaryote; very primitive eukaryote (NO mitochondria)
  • Cpn60 encodes for mitochondrial protein, Giadria has Cpn60 gene but NO MITOCHONDRIA! Ancestor must have had it, but lost theme after lateral gene transfer.
  • Advantage: Nucleus of nucleus taking control of cellular function integration of metabolism, gives nucleus CONTROL
Endosymbiosis: Evidence & Evolution

Possible Reasons for Lateral Gene Transfer

  • Some enzymes/ proteins are TOO BIG to be transferred back into mitochondria are these genes need to be expressed locally.
  • Enzymes/ proteins that are used in the ETC degrade; tightly regulated by redox potential (ETC)
  • Maybe genes can’t be explained in nucleus because mitochondrial genes are different from DNA genes

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