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Bio Sci 97 Part 1 - DNA: Genomes Read1.11.3...

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DNA: Structure and Replication Chapter 1 The Genetic Code of Genes and   Genomes Read 1.1-1.3  Genetics  – study of biologically inherited traits Inheriting traits are determined by genes, elements of heredity, that are transmitted from  parents to offspring’s in reproduction Genetics   Genomics   Molecular genetics Classical Genetics – Mendel Molecular Genetics - DNA 1.1 DNA – molecule of heredity Chromosomes  – thread-like objects inside nucleus Splitting behavior Contain DNA and proteins DNA is constant (amount) per cell Doesn’t seem diverse enough Proteins differ greatly from one cell to another Genetic traits can be altered by treatment within pure DNA Griffith’s Experiment – Transformation of Activity is DNA Suggested component transferred from heat-killed S cell to live R cell is the genetic  material Pneumococcus Type S – polysaccharide capsule hides bacteria from immune system Type R – mutation; lacks polysaccharide capsule Live S – Dies Live R – Lives Heat-killed S – Lives
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Live R + Heat-killed S – dead Heat-killed S must have transformed the live R cell into an S cell – perhaps by  transferring its genetic material, DNA Avery, Macleod, McCarty’s Experiment (1944) Used cell plate – no mouse Showed successful removal of macromolecules Showed that the substance causing the transformation of R cells into S cells was DNA Added DNA isolated from S cells to growing cultures of R cells Few Type S cells were produced Transforming activity was not altered by treatments that destroy either proteins or RNA  (protease and RNase) Transforming activity is destroyed by DNase Transmission of DNA is the link between Generations Hershey and Chase (1952) Blender experiment Studied E. coli after injection by virus T2 Bacteriophage – bacteria eater Used radioactive isotopes T2 – head containing phage DNA, collar, tail, and tail fibers T2 Infection Phage particle’s tail attaches to bacterial cell wall Entry of phage material Multiplication to form progeny phage Release of progeny phage by bursting (lysis) of bacterial host cell DNA – phosphorous from the sugar-phosphate backbone Proteins – sulfur 
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Used radioactive isotopes  32 P and  35 Kitchen blender – swirled violently to separate phage material from cell surface Must tear phage heads from bacterial cell surface DNA is inherited from parental phage Genetic material must enter infected cells very soon after phage attachment 1.2 DNA Structure Watson and Crick – DNA structure Replication Controls hereditary traits – DNA contain genetic information in coded form
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