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AST 309L
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Review for Test 3

AST. 309L - REVIEW FOR TEST #3
  1. Beginnings of Life - Factors Important For f(l)
    1. Basic molecules
      1. Proteins - polymerization of amino acids by peptide bonds, water by product
      2. Nucleic acids -sugar/phosphate chains (H-OH also), joined by bases (nucleotide)
      3. 4 possible bases in groups of 3 (codons), 64 combinations (AGCT: DNA;AGCU: RNA)
      4. A-T  G-C
      5. Codons specify one of 20 amino acids for protein construction
      6. Transcription (DNA->RNA) in nucleus, translation in ribosome in cytoplasm
    2. Ideas on possible mechanisms for synthesis of biological molecules
      1. Monomers - tested in Miller-Urey experiment (maybe too reducing?) made amino acids, formic acid, among other small organic molecules. ribose sugars harder and less stable than amino acids phosphates from soil erosion
      2. Polymers/Proteins - Sydney Fox experiment - heat/evaporation possible importance of clays - take away water, provide structure
      3. Polymers/DNA,RNA - correct bond placement hard for nucleotides Leslie Orgel found metal ions (like zinc) may help
      4. Current polymerization uses ATP for energy input; prob. simpler in past
    3. Transition from molecules to life
      1. Proteins, nucleic acids, cells - one first or all 3 necessary?
      2. Proteins easier to make accidentally, "scrapie"= pure protein disease
      3. Proteinoid microspheres made by S. Fox
      4. Sol Spiegelman found - RNA could replicate in test tube (with "replicase" enzyme); replicase could make RNA by itself also!
      5. Short RNA strands are self-replicating in soup of nucleotides
      6. Very recent exp's; some RNA's can act as own replicase
      7. Cairns-Smith - possible early genetic code in clay
      8. Shapiro - interpreter molecules possible key (join amino acid to tRNA)
      9. Peptide nucleic acid idea; advantages of both proteins and nucleic acids
  2. Unusual Life?
    1. Importance of carbon and water? for chemical life
    2. Non-chemical life?? - interstellar clouds, gravity based, neutron based!
  3. Evolution of Simple Life
    1. Basics
      1. Radioactive Dating - carbon-14 useful for recent hominid bones, but not long-term evolution - concept of half-life
      2. Two million species classified; prob. tens of millions or more
      3. Classification schemes - ...genus, species; or by DNA similarity
    2. Early evolution (pre-Cambrian) and basics of the process
      1. First fossil evidence for life - ~3.8 bil. yr. ago (controversial?)
      2. Progression of simple to more complicated single celled life (handout or p. 87-88)
      3. Keys to evolution - random inheritable traits plus natural selection Mutations can be produced by gene damage, copying errors, ....
      4. Eukaryotic cells much more complex (larger variety of abilities), nucleus and other organelles (some with own DNA), likely followed oxygen increase
      5. Sexual reproduction added much larger variety to possible changes.
    3. Evolution toward Intelligent Life
      1. Species "explosion" at Cambrian era, ~ 550 million yrs ago after a mass extinction, first complex species
      2. Fish, amphibians, dinosaurs/mammals, birds, primates, hominids, ...







 





18 October 2006
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