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Griffith used Diplococcus Pneumonia, a bacteria that occurs in two forms—the s-strain (virulent) and R-strain (non-virulent). Mice were injected with s-strain die from pneumonia, but mice injected with R-strain bacteria continue to live. Moreover, injection with heat-killed s-strain bacteria results in the mice surviving. Griffith then found out that mice injected with a mixture of heat-killed s-strain and live R-strain die from pneumonic infection. In fact, living s-strain bacteria were found in the infected mice. Griffith hypothesized that the R-strain bacteria had somehow been transformed by the heat-killed S-strained bacteria. Oswald Avery, Colin McCleod, and Maclyn McCarty building on Griffith's work, showed that only DNA could cause the transformation. They isolated a cell-free extract from the S-strain bacteria and were able to transform living R-strain into a culture
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Unformatted text preview: containing both S-strain and R-strain cells. The purified extract contained Griffith's "transforming principle". Through biochemical testing, they showed it to be deoxyribonucleic acid (DNA). 1. Removing the protein from the extract of the S strain with organic solvents still allows transformation 2. Digesting the extract with enzymes that destroy protein still allows transformation 3. Treating the extract with ribonuclease (which degrades RNA) still allows transformation 4. Treating the extract with DNase (which degrades DNA) destroys the ability of the extract to transform cells Nucleotide is the sugar, base, & phosphate Nucleoside is the base & sugar w/o phosphate Purines are attached at their N9 position to the 1’ carbon atom of sugar Pyrimidines are attached at their N1 position to the 1’ carbon atom of sugar...
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This note was uploaded on 10/30/2010 for the course CHEM 114C taught by Professor Alexanderhoffmann during the Spring '08 term at UCSD.

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