mohamed nasreldin
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History of DNA. 1. Mohamed Nasreldin. “Transforming Factor”. In 1928, Fredrick Griffith, a British Biologist, did an experiment on mice He injected two strains of bacteria into the mice One was harmful, the other was harmless. 2. “Transforming Factor”. - PowerPoint PPT PresentationTRANSCRIPT
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MOHAMED NASRELDIN
History of DNA1
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In 1928, Fredrick Griffith, a British Biologist, did an experiment on mice
He injected two strains of bacteria into the mice
One was harmful, the other was harmless
“Transforming Factor”2
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He injected Strain 1 (harmful) into the first mouse, it died
The second mouse, he injected Strain 2 (Harmless), it survived
The third mouse, He injected a heat treated Strain 1, the mouse survived
In the fourth mouse he injected a mixture of strain 2 and heat treated strain 1, the mouse died.
“Transforming Factor”3
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“Transforming Factor”4
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Since the fourth mouse died, Griffith concluded that there was a transforming factor.
The harmless strain transformed and became deadly.
“Transforming Factor”5
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American BiologistTook Griffith’s experiments a step furtherWanted to find out what was the transforming
factor.Thought it might be Protein
Oswald Avery6
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Treated Griffith’s mixture of heat-treated deadly strain and live harmless strain with protein-destroying enzymes
The bacteria grown from the mixture was still transformed
He concluded that Protein was not the transforming factor
Avery’s Experiments7
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He then treated the mixture with DNA destroying enzymes
The bacteria colonies did not transformAvery concluded that DNA is the genetic
material
Avery’s Experiments8
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Many scientists did not believe AveryStill believed Protein was the “transforming
factor” because DNA was too simpleFurther research had to be conducted
Further Experiments9
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Wanted to make sure the transforming factor was DNA
Used viruses for testing
Hershey and Chase10
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Knew that the phage had two components- DNA and Protein
They were not sure which one had the hereditary material
Made an experiment to determine which part of the phage it was DNA or the protein
Hershey and Chase11
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For one batch, they used a radioactive isotope of sulfur (found only in Protein)
The other batch they used a radioactive isotope of phosphorus (found in DNA)
Hershey and Chase12
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They concluded that DNA was the hereditary material
Their experiment convinced other scientists that DNA contains the genetic material
Hershey and Chase13
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When the protein coats were labeled, the radioactivity was detected outside the cells
When DNA coats were labeled, the radioactivity was detected inside the cells
Hershey and Chase14
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Bibliography
http://edu.glogster.com/media/4/14/58/61/14586124.jpg
http://www.csb.yale.edu/userguides/graphics/ribbons/help/dna_rgb.gif
http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg
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The END16