by123 chapter 16 - CHAPTER 16 The Molecular Basis of...

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CHAPTER 16: The Molecular Basis of Inheritance Transformation- a change in the genotype and phenotype due to the taking in of external DNA from another cell In Frederick Griffith’s experiment, he studied two strains of bacteria: S cells, which are pathogenic because they have a capsule that protects them from an animals’ defense system. R cells lack a capsule and are nonpathongenic. Griffith injected mice with the cells o Living S cells mouse dies o Living R cells mouse lives o Heat-killed S cells mouse lives o Mixture of heat-killed S cells and living R cells mouse dies, and living S cells are found in its blood o CONCLUSION: the living R bacteria had been transformed into pathogenic S bacteria by an unknown heritable substance from the dead S cells that allowed the R cells to make capsules o The transforming agent was DNA Experiment with a bacteria phage conducted by Hershey and Chase gave more evidence that DNA is the genetic material o A virus is composed of DNA and protein o Protein contains sulfur, and no phosphates. DNA contains phosphates, no sulfur. The experiment uses dyes to identify the components. o Sulfur (protein) does not go into the bacteria in which the virus injects its genes into, but phosphorus (DNA) does o DNA, not protein, is the genetic material DNA- deoxyribose nucleic acid o DNA consists of nucleotides, which are a nitrogenous base, sugar, and phosphate
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by123 chapter 16 - CHAPTER 16 The Molecular Basis of...

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