lect2 - Lecture 2 (FW) January 26, 2009 DNA is a double...

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Lecture 2 (FW) January 26, 2009 DNA is a double helix. Replication. Mitosis Reading assignment: DNA structure and replication, pp. 81-104. Cell structure review, pp. 19-26. Mitosis, pp. 31-36. Lecture 2. DNA is a double helix of polynucleotides. Primary goal: The structure of DNA and how it was discovered. Why is this important? It is the key to understanding the functions of a gene: heredity and governance of the cell. I. The conundrum A. DNA seemed too simple to encode information carried by genes. DNA is a polymer of nucleotides, of which there are only 4 kinds, A,G, T and C . Yet, the bacterial transformation, and other kinds of experiments, clearly pointed to DNA. B. The most complex type of molecule in cells is protein , composed of 20 different kinds of amino acids ( monomer ) strung together in a polymer ( protein or polypeptide). C. Polymers are molecules in which similar repeating units (monomers) are strung together , held by chemical bonds, like beads on a string. Plastics ( acrylamides) and fibers ( nylon) are polymers. So are proteins and nucleic acids. There are also polymers of sugar monomers found in cells, called polysaccharides. II. Would an understanding of the 3D structure of DNA provide a clue about how it could encode and transmit genetic information? The answer to that question, published in 1953, astonished the scientific community, and is the bedrock to the “new biology”. A. The players:
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lect2 - Lecture 2 (FW) January 26, 2009 DNA is a double...

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