CHAPTER 12

CHAPTER 12 - CHAPTER 12 DNA: THE CARRIER OF GENETIC...

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CHAPTER 12 DNA: THE CARRIER OF GENETIC INFORMATION EVIDENCE OF DNA AS THE HEREDITARY MATERIAL Several early clues to the role of DNA were not widely noticed DNA is the transforming principle in bacteria Frederick Griffith o S cells exhibited virulence and killed mice it was injected into Ability to cause disease in its host o Heated S cells did not kill mice o R cells exhibited avirulence and didn’t kill mice it was injected into Inability to cause disease in its host o When heated S cells and R cells were both injected, the mice died Both did not kill on their own Something caused transformation in R cells Permanent genetic change in which the properties of one strain of dead cells are conferred on a different strain of living cells Oswald Avery discovered that it was the DNA that transformed the R cells DNA is the genetic material in certain viruses Alfred Hershey and Martha Chase did an experiment on bacteriophages (phages) o Viruses that infect bacteria Labeled the protein of one sample with 35S and DNA of another sample with 32P Bacteriophages in each sample attached to bacteria Researchers shook them off the bacteria by agitating them Centrifuged the cells 35S was still present in the solution o It had not entered the cell 32P was not present in the solution o It had entered the cell Concluded that bacteriophages inject their DNA into bacterial cells, leaving most of their protein on the outside THE STRUCTURE OF DNA James Watson and Francis Crick o Integrated all the available information into a model that demonstrated
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how the molecule can both carry information for making proteins and serve as its own template for its duplication Pattern or guide Nucleotides can be covalently linked in any order to form long polymers Each DNA building block is a nucleotide consisting of the pentose sugar deoxyribose , a phosphate, and one of four nitrogenous bases o Four bases Two purines Adenine (A) and guanine (G) Two pyrimidines Thymine (T) and cytosine © The 3’ carbon of one sugar is bonded to the 5’ phosphate of the adjacent sugar to
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This note was uploaded on 04/04/2008 for the course BIO 101 taught by Professor Martin during the Fall '08 term at Rutgers.

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CHAPTER 12 - CHAPTER 12 DNA: THE CARRIER OF GENETIC...

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