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Biology Exam1 chapter 12 part 2

Biology Exam1 chapter 12 part 2 - TEXTBOOK NOTES FOR THIRD...

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TEXTBOOK NOTES FOR THIRD SECTION OF COURSE Chapter 12: DNA: The Carrier of Genetic Information Evidence of DNA as the Hereditary Material pg. 261 o Scientists originally thought proteins were the genetic material o DNA is the transforming principle in bacteria pg. 261 Griffith: two strains of bacteria S strain: virulence: ability to cause disease R strain: avirulence: inability to cause disease o R cells: mouse lives o S cells: mouse dies o Heat killed S cells: mouse lives o It seemed something in the heat killed virulent cells converts avirulent cells to lethal form Transformation: type of permanent genetic change in which the properties of one strain of dead cells are conferred on a different strain of living cells 1944: Avery, MacLeod, McCarty: identified DNA as the transforming principle Lysed S cells and separated cell contents into fractions o DNA is the genetic material in certain viruses pg. 263 1952: Hershey and Chase Studies involving bacteriophages (viruses that infect bacteria) and their reproduction o Reproduce inside a bacterial cell and eventually cause the cell to break open and release large numbers of new viruses The Structure of DNA pg. 263 o 1953: Watson and Crick Proposed model for structure of DNA Integrated all available information into model that demonstrated how the molecule can both carry information for making proteins and serve as its own template for duplication o Nucleotides can be covalently linked in any order to form long polymers pg. 263 DNA building block is nucleotide Nucleotide: consists of pentose sugar deoxyribose, phosphate, one of 4 nitrogenous bases o Bases: two purines (adenine, A and guanine, G) and two pyrimidines (thymine, T and cytosine, C) Nucleotides are linked by covalent bonds to form alternating sugarphosphate backbone o 3’ carbon of one sugar is bonded to 5’ phosphate of the adjacent sugar to form a 3’,5’ phosphodiester linkage Most DNA molecules found in cells are millions of bases long DIAGRAM pg. 264 DNA strand is directional o One end (5’ end) has a 5’ carbon attached to a phosphate o Other end (3’ end) has a 3’ carbon attached to a hydroxyl group
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1949: Chargaff Ratios of purines to pyrimidines and also adenine to thymine and guanine to cytosine were not far from 1 Known as Chargaff’s rules o DNA is made of two polynucleotide chains intertwined to form a double helix pg. 264 1951 – 1953: Franklin
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Biology Exam1 chapter 12 part 2 - TEXTBOOK NOTES FOR THIRD...

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