section 12.1. * 1928 british scientist – frederick griffith * wanted to know how bacteria made...
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Section 12.1
*Identifying the substances in genes
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*1928 British scientist – Frederick Griffith
*Wanted to know how bacteria made people sick, especially pneumonia
*Griffith isolated 2 types of pneumonia bacteria:
*S strain – harmful bacteria, smooth edges
*R strain – harmless bacteria, rough edges
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*Griffith’s Experiment
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*WHAT HAPPENED???
*Somehow the heat killed bacteria passed the ability to cause disease to the harmless strain of bacteria
*Transformation = one type of bacteria (harmless) had been permanently changed into another (harmful)
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*Oswald Avery*1944 Canadian scientist Oswald Avery
*Wanted to determine which molecule in the heat-killed bacteria was most important for transformation
*EXPERIMENT
*Extracted a mixture of various molecules from the heat killed bacteria.
*They treated the mixture with enzymes that destroyed proteins, lipids, carbohydrates, and nucleic acids
*RESULTS
*Transformation still occurred
*None of the molecules mentioned above could have been responsible since they were destroyed
*Except…. When DNA was destroyed. Transformation could NOT occur
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*Hershey and Chase *Studied Viruses, more specifically bacteriophages (virus that infects
bacteria)
*They wanted to know which part of the virus – the protein coat or the DNA core – entered the bacterial cell
*EXPERIMENT
*Grew cultures of viruses in radioactive isotopes
*DNA was marked with phosphorus
*Protein was marked with sulfur
*RESULTS
*Genetic material of the bacteriophage was DNA and not protein
*They convinced other scientists that DNA was the genetic material found in genes in all living things!
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*Hershey and Chase
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*The Role of DNA*Store information
*Copy information
*Transmit information