chapt14_lecture - DNA: The Genetic Material Chapter 14 The...

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DNA: The Genetic Material Chapter 14
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2 The Genetic Material Frederick Griffith, 1928 studied Streptococcus pneumoniae , a pathogenic bacterium causing pneumonia there are 2 strains of Streptococcus : - S strain is virulent - R strain is nonvirulent Griffith infected mice with these strains hoping to understand the difference between the strains
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3 The Genetic Material Griffith’s results: - live S strain cells killed the mice - live R strain cells did not kill the mice - heat-killed S strain cells did not kill the mice - heat-killed S strain + live R strain cells killed the mice
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6 The Genetic Material Griffith’s conclusion: - information specifying virulence passed from the dead S strain cells into the live R strain cells - Griffith called the transfer of this information transformation
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7 The Genetic Material repeated Griffith’s experiment using purified cell extracts and discovered: - removal of all protein from the transforming material did not destroy its ability to transform R strain cells - DNA-digesting enzymes destroyed all transforming ability - the transforming material is DNA
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8 The Genetic Material Hershey & Chase, 1952 - investigated bacteriophages : viruses that infect bacteria - the bacteriophage was composed of only DNA and protein - they wanted to determine which of these molecules is the genetic material that is injected into the bacteria
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9 The Genetic Material - Bacteriophage DNA was labeled with radioactive phosphorus ( 32 P) - Bacteriophage protein was labeled with radioactive sulfur ( 35 S) - radioactive molecules were tracked - only the bacteriophage DNA (as indicated by the 32 P) entered the bacteria and was used to produce more bacteriophage - conclusion: DNA is the genetic material
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11 DNA Structure DNA is a nucleic acid . The building blocks of DNA are
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chapt14_lecture - DNA: The Genetic Material Chapter 14 The...

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