Assignments
• Watch Crash Course Big History #4, Life Begins
• Watch the videos What is a Molecule? and Your Body's Molecular Machines, at How Scientists Know About Molecules.
• Watch the video What is a Gene?, at How Scientists Know About Genes.
• Watch this quick tutorial about the Central Dogma of Molecular Biology, which describes the flow of genetic information in a cell: a DNA gene (a coded recipe for a protein) is transcribed into a messenger RNA (a portable form of the recipe), and in turn, the messenger RNA is translated into protein (a chain of amino acids) which carries out a specific function. An example is the hemoglobin gene, which code for a chain of the protein hemoglobin; chains assemble into hemoglobin molecules, whose function is to transport oxygen from lungs to tissues.
Here's a minimalist summary of the Central Dogma:
• Before each class, check the appropriate episode page(s) for Assignments, things To Think About, More Resources. Also and the day before class, check Your Questions. To be sure that your own question or comment is considered for the upcoming Monday class, submit it at least 24 hours beforehand (Sunday morning). Late questions will still be posted and perhaps taken up in a later class.
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To Think About
• Could the most basic molecules of life still be spontaneously arising on Earth? If so, why don't they accumulate and start becoming more complex, perhaps producing life forms competing with our kind of life?
• Do you find it plausible that the enormously complex molecular machinery of life could have emerged spontaneously from simpler molecules, just from the tendency of more stable molecules to persist, and from the possibilities that arise from self-copying?
• A recurring theme of Crash Course Big History is increasing complexity. Is the universe as a whole, on it grandest scales, becoming more complex? Where do we find the greatest complexity? What is complexity, anyhow?
• The simplest proteins are single chains of building blocks (called amino acids) of which there are 20 different ones. When a cell builds a protein, it can theoretically put any one of the 20 building blocks in the first position of the chain, any one of the 20 in the second position, and so forth. How many different "proteins" of length 6 building blocks are theoretically possible? (answer: 64 million) How many proteins of length 62 building blocks are possible? The average number of building blocks in proteins is about 300! The range is from under 100 to around 30,000.
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More Resources
• The How Scientists Know pages mentioned above contain some very good resources on how scientists learn the structures of molecules, and how they learn and compare genes within and among organisms to establish evolutionary relationships (about which more in Episode 5).
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Your Questions
Shortly before each class, check Your Questions for the episode(s) assigned. Submit your questions using the form at the bottom of this and every page at the Big Bang, Then What? website.
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