Chapter 16

Chapter 16 - Chapter 16: The Molecular Basis of Inheritance...

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Chapter 16: The Molecular Basis of Inheritance 16.1: DNA and Genetic Material - Evidence that DNA can transform bacteria o Griffith mixed two strands of Heated pathogenic (harmful) and one non pathogenic (harmless) The heated pathogenic= dead Result: some of the non pathogenic living cells became pathogenic Conclusion: some chemical component of the dead pathogenic cells caused this heritable change Griffith called this “transformation” - Evidence that viral DNA can program cells o Phages- viruses that eat bacteria o Hershey and Chase’s experiment Result: radioactive phage DNA in pellet and radioactive phage proteins in liquid Conclusion: DNA functions as the genetic material of phage T2. - Evidence that DNA is genetic material o Chargaff noticed that base composition of DNA varies from one species to another>>molecular diversity o He also noticed the ratio of nucleotide bases o Chargaff’s rule= A-T and G-C o 5 end at phosphate and 3 end at the OH - Building a Structural Model of DNA: Scientific inquiry o Rosalind Franklin-photograph of DNA o Watson and Crick studied the photos and discovered that… DNA= helical shape Certain width b/w helix and nitrogenous base All together= double helix!! o Built double helix DNA Bases= hydrophobic and held by hydrogen bonds ( that’s why they are faced inward) Sugar phosphate backbone Anti-parallel Van der waals= holding molecules together 16.2: Many proteins work together in DNA replication and repair - DNA replication: Closter look o Semi-conservative model: two strands of parental molecule separate and each function as a template for synthesis of a new complementary strand. o Origin of replication- where DNA replication starts o Prokaryotes Circular and has a single origin Forms a bubble so that DNA goes both directions until the entire molecule is copied o Eukaryotes Have hundreds of origins Multiple bubbles in both directions Thus, speeds up replication o At each end of origin= replication fork Where parental DNA is being unwound
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Helicase= enzyme that untwists DNA to separate the parental cells making them available as template strands Single strand binding protein- bind to unpaired DNA strands to stabilize them Untwisting of double helix causes tighter twisting and strain ahead of the replication fork
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This note was uploaded on 01/09/2012 for the course BIO 105 taught by Professor Any during the Fall '09 term at Maryland.

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Chapter 16 - Chapter 16: The Molecular Basis of Inheritance...

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