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ORIGINS OF HEREDITY
Pages 287-290
FIRST GENETIC MATERIAL
•RNA is thought to have been the first heredity molecule
•Evidence:
•Can make many shapes
•Some RNA, called ribozymes, can replicate themselves
•Quite a few viruses use RNA instead of DNA such as Ebola and
measles
FIRST GENETIC MATERIAL
•It is hypothesized that this RNA started to evolve inside cell-like
structures made of proteins, amino acids, and lipids
•Then the RNA started to direct the cell
THE FIRST CELLS
•Prokaryotes came before eukaryotes
•The first cells did not use oxygen (it was toxic to them), and
depended on the organic molecules (primordial soup: think Oparin)
in the environment for food
•Later photosynthetic cells evolved and put oxygen into the
atmosphere
•Oxygen prevented further Spontaneous Generation
THE FIRST CELLS
•Order of major events in cell evolution
• Anaerobic  Aerobic
• Heterotrophic  Autotrophic
• Chemosynthetic  Photosynthetic
• Don’t use oxygen  use oxygen
• Don’t make own food  make own food
•Energy comes from chemicals energy comes from sunlight
THE FIRST EUKARYOTES
THINK ABOUT IT
What knowledge do we have about mitochondria and chloroplasts that provide
evidence that they might have lived independently at one point?
THE FIRST EUKARYOTES
Endosymbiosis Theory
•Mitochondria and chloroplasts are thought to have once been
prokaryotic cells that were engulfed by a bigger prokaryotic cell
•Supporting Evidence:
•Both organelles contain their own DNA
•DNA is circular (like other prokaryotes)
•Replicate on their own