CH11 - UNIT III. Genetics Chapter 11 Nucleic Acid Structure...

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1 UNIT III. Genetics Chapter 11 Nucleic Acid Structure and DNA Replication
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2 Student Learning Outcomes: Describe the experiments that demonstrated that DNA is the genetic material. Explain how the contributions of Wilkins and Franklin, Watson and Crick, and Chargaff resulted in understanding the structure of DNA. Explain the results of the Meselson-Stahl experiment and describe the predicted results if DNA replication followed the other possible models. Outline the basic steps involved in DNA replication, including major differences between eukaryotes and bacteria.
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3 Genetic material must be able to: Contain the information necessary to construct an entire organism Pass from parent to offspring and from cell to cell during cell division Be accurately copied Account for the known variation within and between species
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4 Late 1800s scientists postulated a biochemical basis Researchers became convinced chromosomes carry genetic information 1920s to 1940s expected the protein portion of chromosomes to be the genetic material
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5 Griffith’s bacterial transformations Late 1920s Frederick Griffith was working with Streptococcus pneumoniae S. pneumoniae Strains that secrete capsules look smooth and can cause fatal infections in mice Strains that do not secrete capsules look rough and infections are not fatal in mice
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6 Rough strains (R) without capsule are not fatal No living bacteria found in blood Smooth strains (S) with capsule are fatal Capsule prevents immune system from killing bacteria Living bacteria found in blood If mice are injected with heat-killed type S, they survive Mixing live R with heat- killed S kills the mouse Blood contains living S bacteria Transformation
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7 Genetic material from the heat-killed type S bacteria had been transferred to the living type R bacteria This trait gave them the capsule and was passed on to their offspring Griffith did not know the biochemical basis of his transforming principle
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Avery, MacLeod, and McCarty used purification methods to reveal that DNA is the genetic material 1940s interested in bacterial transformation Only purified DNA from type S could transform type R Purified DNA might still contain traces of contamination that may be the transforming principle Added DNase, RNase and proteases RNase and protease had no effect With DNase no transformation DNA is the genetic material
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9 Hershey and Chase 1952, studying T2 virus infecting Escherichia coli Bacteriophage or phage Phage coat made entirely of protein DNA found inside capsid
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10 Shearing force from a blender will separate the phage coat from the bacteria 35 S will label proteins only
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This note was uploaded on 04/06/2010 for the course BIO bio 183 taught by Professor Ferzli during the Spring '08 term at N.C. State.

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CH11 - UNIT III. Genetics Chapter 11 Nucleic Acid Structure...

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