Chapter 11 & 12

Chapter 11 & 12 - Chapter 11 Bio 122-A Fall 2010 Dr....

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Chapter 11 Bio 122-A Fall 2010 Dr. Anandan Outline 11.1 Biochemical identification of the genetic material 11.2 Nucleic acid structure 11.3 An overview of DNA replication Pages 215-232 only 1 Anandan Bio 122 Fall 2010
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2 11.1 Genetic material must meet criteria: 1. Information 2. Replication 3. Transmission 4. Variation Anandan Bio 122 Fall 2010
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3 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 Anandan Bio 122 Fall 2010
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4 11.1 Griffith’s bacterial transformation 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 Anandan Bio 122 Fall 2010
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5 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 Anandan Bio 122 Fall 2010
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6 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 Anandan Bio 122 Fall 2010
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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 7 Anandan Bio 122 Fall 2010
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8 Anandan Bio 122 Fall 2010
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9 11.1Hershey and Chase 1952, studying T2 virus infecting Escherichia coli Bacteriophage or phage Phage coat = capsid = made entirely of protein DNA found inside capsid Anandan Bio 122 Fall 2010
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10 Anandan Bio 122 Fall 2010
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11 Shearing force from a blender will separate the phage coat from the bacteria 35 S will label proteins only 32 P will label DNA only Experiment to find what is injected into bacteria- DNA or protein? Results support DNA as the genetic material Anandan Bio 122 Fall 2010
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12 11.2 Levels of DNA structure 1. Nucleotides are the building blocks of DNA (and RNA). 2.
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This note was uploaded on 02/13/2011 for the course BIO 122 taught by Professor Anandan during the Fall '08 term at Drexel.

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Chapter 11 & 12 - Chapter 11 Bio 122-A Fall 2010 Dr....

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