rav65819_ch14_255-276

rav65819_ch14_255-276 - ; 14 chapter D NA: The Genetic...

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chapter DNA: The Genetic Material introduction THE REALIZATION THAT PATTERNS OF heredity can be explained by the segregation of chromosomes in meiosis raised a question that occupied biologists for over 50 years: What is the exact nature of the connection between hereditary traits and chromosomes? This chapter describes the chain of experiments that led to our current understanding of DNA, modeled in the picture, and of the molecular mechanisms of heredity. These experiments are among the most elegant in science. And, just as in a good detective story, each discovery has led to new questions. But however erratic and lurching the course of the experimental journey may appear, our picture of heredity has become progressively clearer, the image more sharply defined.
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14.4 Prokaryotic Replication concept outline 14.1 The Nature of the Genetic Material Grif th nds that bacterial cells can be transformed f f Avery, MacLeod, and McCarty identify the transforming principle Hershey and Chase demonstrate that phage genetic material is DNA 14.2 DNA Structure DNA’s components were known, but its three-dimensional structure was a mystery Chargaff, Franklin, and Wilkins obtained some structural evidence The Watson–Crick model t the evidence available f 14.3 Basic Characteristics of DNA Replication Meselson and Stahl demonstrate the semiconservative mechanism The replication process: An overview Prokaryotic replication starts at a single origin E. coli has at least three different DNA polymerases Unwinding DNA requires energy and causes torsional strain Replication is semidiscontinuous Synthesis occurs at the replication fork The replisome contains all the necessary enzymes for replication 14.5 Eukaryotic Replication Eukaryotic replication requires multiple origins The enzymology of eukaryotic replication is more complex Linear chromosomes require different termination 14.6 DNA Repair
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Cells are constantly exposed to DNA-damaging agents DNA repair restores damaged DNA Repair can be either speci c or nonspeci c f f 255 rav65819_ch14_255-276.indd 255 rav65819_ch14_255-276.indd 255 11/16/06 5:46:19 PM 11/16/06 5:46:19 PM 14.1 The Nature of the Genetic Material In the previous two chapters, you learned about the nature of inheritance and how genes, which contain the information to specify traits, are located on chromosomes. This finding led to the question of what part of the chromosome actually contains the genetic information. Specifically, biologists wondered about the chemical identity of the genetic information. They knew that chromosomes are composed primarily of both protein and DNA. Which of these organic molecules actually comprises the genes? Starting in the late 1920s and continuing for about 30 years, a series of investigations
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This note was uploaded on 10/15/2010 for the course BIO BIO1 taught by Professor Lipke during the Fall '09 term at CUNY Brooklyn.

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rav65819_ch14_255-276 - ; 14 chapter D NA: The Genetic...

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