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  1. Astrobiology Replicators

  2. NASA’s Astrobiology Page •

  3. The Legos of Life • This is review: • What are the Legos? • How did the Legos make it to Earth (as well as planets throughout the Universe)?

  4. The Legos of Life (Continued) • What are the Legos (molecules) that life needs (think back to your biology)? • Amino acids: “NASA and University Researchers Find a Clue to How Life Turned Left” • • Amino acids are found in a lot of celestial bodies (including meteoroids and comets).

  5. The Legos of Life (Continued) • Life on Earth uses 20 amino acids to build proteins. • Common amino acids include: glycine, alanine, and glutamic acid. • Other amino acids that Earth’s life does not use have also been found (e.g. isovaline and pseudoleucine).

  6. The Legos of Life (Continued) • Glycoaldehyde – a two carbon monosaccharide that has been detected in the interstellar medium. • It is made from the amino acid glycine (which has been found on meteorites, asteroids, and comets. • What very important molecule is a sugar? • Deoxyribose and ribose are also monosaccharides

  7. Analysis of Meteorite

  8. What are Purines and Pyrimidines? • Nitrogenous bases used in DNA and RNA to code for proteins. They are the building blocks of genes!

  9. The Legos of Life (Continued) • One more really cool thing. What are these?

  10. Assembling the Legos • Questions: • Is evolution, the natural force, confined to only biological life? • So, what is evolution (what are the requirements for evolution to take place)? • Answers: • No, it is not confined to living organisms. • In simplest terms: Descent with Modification

  11. The Requirements of Evolution • What are the necessary constituents of evolution (what factors need to be present for evolution to occur)? • You need replicators capable of autocatalysis. • What kinds of replicators do you know? • You need some type of inheritance (characteristics passed along from one generation to another). • You need the occasional mistake in replication. • What is this known as?

  12. One Final Requirement • There is one final thing that is necessary for descent with modification to take place, what is it? • A differential selection process. What is this known as? • Natural Selection – more replicators are made each generation than can survive. The best adapted, to their environment, replicators are typically those that survive.

  13. The Force Known as Evolution • Evolution is an observable phenomenon and behaves the same way wherever you happen to find yourself. • It is comparable to gravity – it happened yesterday, it is happening right now (today), and it will happen tomorrow the same way. • Astrobiology is evolution writ large!

  14. How were the Legos Put Together • This is the question we are trying to answer. • We have all of the Legos but we are “looking for the instructions.” • What is a good candidate for first replicator? • Not DNA, which is very complex, but simpler RNA. • What do you know about RNA? How many kinds of RNA are there? • In biology class we learn only about three. What are they?

  15. RNA Compared w/ DNA

  16. RNAs involved in protein synthesis

  17. RNAs involved in post-transcriptional modification or DNA replication

  18. Regulatory RNAs

  19. Parasitic RNAs

  20. RNA World Hypothesis

  21. Strengths of RNA World Hypothesis • RNA can act as: • Hereditary material • Coding material • And can have catalytic (including autocatalytic) activity. • RNA can act as its own enzyme.

  22. Weakness of RNA World Hypothesis • We still have not found a clear pathway from the “RNA World” to a world that includes RNA and proteins. • A strength of the RNA World hypothesis is also a weakness. • RNA polymers are fragile (though in a vesicle they would be protected).

  23. Important Questions Being Studied • How did RNA polymerases emerge? • RNA polymerase is necessary to create RNA chains (this is an important question with respect to autocatalysis). • How were RNA molecules incorporated into membranes?

  24. RNA World Hypothesis