AST 248: The Search for Life in the Universe

1. What two assumptions of the Miller-Urey experiment for monomer production on the early Earth are probably incorrect? The atmosphere of the Earth was more mildly reducing than they assumed, i.e., no CH₄ or NH and little H₂, and monomers are probably more efficiently produced near hydrothermal vents than in the atmosphere.
2. What common material could have been responsible for the first polymerizations of amino acids into proteins? clay
3. Give 2 examples of inorganic self-assemblers with strong reversible bonds. Why are these examples interesting in the context of the origin of life? bubbles, clay
4. What is the importance of surface tension to the origin of life? It takes energy to make a surface or boundary between organic polymers and water. Increasing the surface tension increases the tendency to form large droplets, since large droplets have less surface area than smaller ones if the total volume of all droplets is equal.
5. Perform a brief web survey concerning molecular or genetic clocks in order to answer these three questions.
   1. What is the fundamental flaw in the original assumption of Zuckerkandl and Pauling underlying the original idea of genetic clocks? They assumed that changes to DNA occurred at a uniform rate.
   2. How are molecular clocks calibrated? DNA changes in species of known origination ages from the fossil record establish the mutation rate.
   3. What is the consensus of opinion on the accuracy of molecular clocks? This is a highly controversial subject with wide-ranging opinions; there is no consensus as to their accuracy.
6. This question concerns Mitochondrial Eve and Y-chromosome Adam.
   1. What do these terms mean? They represent the last common ancestor of humans living today along the matrilineal and patrilineal descents, respectively.
   2. About how long ago did they live? Mitochondrial Eve lived about 140,000 years ago; Y-chromosome Adam lived about 60,000-90,000 years ago.
   3. Were either of these individuals the most recent common ancestor of all humans alive now? No, that person lived about 1500 years ago.