Lecture 12 SLIDES

Lecture 12 SLIDES - ANNOUNCEMENTS - Monday, March 1st...

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ANNOUNCEMENTS - Monday, March 1st Midterm # 2 KEY posted in Urey Hall hallway. CAPE reviews this week. I would greatly appreciate your feedback. Problem Set 5 now posted on website – final set! The Molecular Basis of Inheritance Chapter 16 In 1953, James Watson and Francis Crick shook the world with an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA Figure 16.1 DNA - the center of life
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Solving the Structure of DNA DNA Replication Hereditary information – Is encoded in the chemical language of DNA and reproduced in al the cel s of your body The DNA program – directs the development of many different types of traits DNA is the Genetic Material The Search for the Genetic Material • The role of DNA in heredity – Was first worked out by studying bacteria and the viruses that infect them
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Frederick Griffith (1928) Mixed heat-kil ed pathogenic strain (S) with living non pathogenic strain (R). Some living R cel s became pathogenic (like S cel s)! Living S cel s Living R cel s Heat-kil ed S cel s Mixed heat-kil ed S and living R cel s Mouse dies Mouse healthy Mouse healthy Mouse dies Living S cel s are found in blood sample. Figure 16.2 The Search for the Genetic Material: I. Evidence that DNA can transform bacteria Griffith cal ed the phenomenon transformation Now defined as a change in genotype and phenotype due to the assimilation of external DNA by a cel Avery, MacLeod and McCarty (1944) Purified DNA as the pathogenic molecule from kil ed bacteria Transformation The Search for the Genetic Material: II. Evidence That Viral DNA Can Program Cells Additional evidence for DNA as the genetic material came from studies of a virus that infects bacteria Bacteriophages are viruses that infect bacterial cel s Figure 16.3 Phage head Tail Tail fiber DNA Bacterial cel 100 nm Radioactivity (phage protein ) in liquid Phage Bacterial cel DNA Centrifuge Pel et (bacterial cel s and contents) Radioactivity (phage DNA ) in pel et Alfred Hershey and Martha Chase (1952) Showed that DNA is the genetic material of phage T2 The Search for the Genetic Material: II. “the Hershey-Chase Experiment” Figure 16.4 Radioactive- labeled protein Radioactive- labeled DNA 1 2
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DNA is a polymer of nucleotides : 1. a nitrogenous base, 2. a sugar, and 3. a phosphate group Sugar-phosphate backbone Nitrogenous bases 5 ! end O– O P O CH2 5 ! 4 ! O– H H O H H H 3 ! 1 ! H O CH3 N O N H Thymine (T) O O P O O– CH2 H H O H H H H N N N H N H H Adenine (A) O O P O O– CH2 H H O H H H H H H H N N N O Cytosine (C) O O P O CH2 5 !
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Lecture 12 SLIDES - ANNOUNCEMENTS - Monday, March 1st...

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