LS11centerdogma - Lecture 11 Viruses the New Central Dogma Central Dogma of Molecular Biology Pulse-Chase Experiments DNA and RNA viruses

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1 Lecture 11: Viruses & the New Central Dogma Central Dogma of Molecular Biology Pulse-Chase Experiments DNA and RNA viruses Modification of Central Dogma Central Dogma* of Molecular Biology DNA RNA Protein ( genome ) *Attributed to J. Watson by F. Crick Transcription Translation Replication
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2 How is genetic information contained in the DNA processed into usable information? The first experiments to shed light on this process used a technique commonly referred to as a Pulse-Chase Experiment. Isotopes: Atoms that contain the same number of protons but different number of neutrons Radioisotopes Radioisotopes: Isotopes that can decay and emit electromagnetic radiation
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3 two isotopes of hydrogen: Radioisotopes often used in molecule biology: 1 H Non radioactive 3 H radioactive 31 P/ 32 P , 32 S/ 35 S, 12 C/ 14 C , Radioactive isotopes ( radioisotope ) are widely used in molecular biology studies because they are physically distinguishable but chemically identical from each other. Presence of various particles emitted during decay of a radioisotope can be detected by: - Geiger counter (monitor) -exposure to X-ray film (autoradiography)
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4 Pulse-Chase Experiments Pulse - short exposure to labeled precursors Synthesis of DNA, RNA or protein involves the polymerization of precursor molecules (nucleotides or amino acids). If these precursors are radioactively labeled and supplied to cells in a culture media, then the cells will transport them into the cell and use them to synthesize the macromolecule. If cells are examined immediately for the location of the radioactivity, the site of synthesis can be determined. Position of macromolecules in cell are fixed and free *aa are washed away. Autoradiogram detects location of labeled protein .
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5 X-ray film is dark where radioactive emissions are detected. In this experiment, protein synthesis is detected in the cytoplasm but not the nucleus. The Chase Experiment Wash or dilute out label and allow the cell to continue growing for a period. During this period no new incorporation of radioactive precursor in macromolecule occurs; however, macromolecules may move around in the cell ( determines final location of macromolecule).
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6 Presence of radioactivity in nucleus suggests
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This note was uploaded on 01/16/2010 for the course LIFESCI Life scien taught by Professor Lorenz,t.c. during the Fall '09 term at UCLA.

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LS11centerdogma - Lecture 11 Viruses the New Central Dogma Central Dogma of Molecular Biology Pulse-Chase Experiments DNA and RNA viruses

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