AST 309LSpring 2007Review Questions for Second ExamA. Molecules of Life: what are they, what are they made of, how do they interact?1. Give a schematic representation of proteins and nucleic acids, identifying the parts.Draw the chemical process of peptide bond formation.2. Define what a “codon” is and describe its purpose.3. How are proteins made under the direction of DNA? Clearly describe transcription andtranslation. Starting with a DNA codon, TCC, transcribe it into the mRNA codon andtranslate it into the corresponding amino acid. Identify one mutation to the mRNA thatwould not cause a change in the amino acid.4. Be able to identify basic molecules needed for life from diagrams or chemical formulae.B. Origin of Life: understand the problems and the different ideas for solvingthem.1. What are the three basic steps needed to get from simple molecules (like H2O, NH3, andCH4) to a primitive life form?2. What is Strecker synthesis? Explain the synthesis of glycine in the Miller-Ureyexperiment. What criticisms question the relevance of the Miller-Urey experiment?Describe some other possible ways to get monomers on the early Earth.3. What difficulty is encountered when we try to understand how polymers of amino acidsarose on the early Earth? How does Sidney Fox argue that this difficulty was overcome?4. Explain the difficulty in making nucleic acids on the early Earth. How do the experimentsof Leslie Orgel partially overcome these difficulties?5. Describe the two general categories of theories for the transition to life. Which categorywould be favored by considerations of probability theory?6. Describe the “evolution in a test tube” experiments of Sol Spiegelman. Whatimplications do these experiments have for the transition to life?7. Outline the standard picture of the origin of life by chemical evolution on Earth. Discussthe proteins-first and nucleic-acids-first scenarios. Discuss the pros and cons of eachscenario, including recent developments.8. Describe the idea of the origin of life by chemical evolution in space, including evidencethat molecules relevant to the origin of life have been delivered to Earth from space.9. Explain the ideas of A. G. Cairns-Smith regarding the origin of life.10. Explain Shapiro’s idea for the transition from protolife to life with both proteins andnucleic acids, based on the interpreter molecules.11. Describe the RNA world as a nucleic-acids-first scenario. Why is this the most popularscenario now? What are the pros and cons for this picture?12. Describe the scenario of de Duve for a thioester-based protolife that precedes and leads tothe RNA world.13. Discuss the arguments for and against exotic life forms based on Si instead of C, othersolvents, etc.14. Give your estimate for fl and explain your reasoning.C. Survey of our Solar System for Sites for Life: understand atmospheric evolution,greenhouse effect, the Viking experiments, and new developments1. What atmospheric gases contribute to the greenhouse effect?2. Describe the properties of Venus and explain how it developed into its current (very hot)state.3. What implications does the fate of Venus have for the concept of the habitable zone andyour estimate of ne or fl?4. Describe the properties of Mars and explain how it evolved to its current (cold) state. Howwould its evolution affect your estimate of ne or fl ?5. Explain how each of the life detection experiments on Viking worked, what they found,and how the results were interpreted.6. Describe the Martian meteorite, ALH84001. What is its history, and how did it get to Earth? What is the evidence in the meteorite that bacteria once lived on Mars? Why is this interpretation not universally accepted?7. Describe recent results from probes sent to Mars and their implications for Mars as a possible site for life.8. Describe the Sagan/Salpeter ideas for life on Jupiter.9. Describe the conditions found on Europa and Titan and explain why they may beinteresting for life. Describe the results of the Huygens probe of Titan.10. Describe the various methods that can be used to search for evidence of past or currentlife on planets in our solar system. How can we search for (non-intelligent) life in otherplanetary systems?11. Study one of the space missions to another planet in detail, using class notes, the book,and relevant websites. This could be a current mission, a past mission, or a future mission.Report on the instruments and what was, or will be, learned and how these things mightrelate to the issues of the class.Broader Questions1. Describe the increase in complexity at the microscopic level from simple molecules to life.Consider a hydrogen atom in a water molecule in the ocean of the early Earth. Construct aplausible story about how it wound up in a protein in an early life form.2. What are the primary remaining problems in understanding the origin of
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