Genetics380_DNA2009sm_3slides

Genetics380_DNA2009s - Topic DNA structure replication and repair Reading.1-12.3 and 18.2-18.4 DNA as the source of genetic information The

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10/19/09 1 Topic: DNA structure, replication, and repair Reading: Chapters 10, 12.1-12.3, and 18.2-18.4 DNA as the source of genetic information: The discovery of the transforming principle Fred Griffith, 1928 The method The experiment The controls The interpretation DNA as the source of genetic information: Identification of the transforming principle 1944: Avery, MacLeod, McCarty What are the predictions if the “transforming” genetic material is RNA, Protein, or DNA?
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10/19/09 2 DNA as the source of genetic information: Identification of the transforming principle Genes can be transferred between bacteria through “transformation.” Horizontal (versus vertical) gene transfer. Antibiotic resistance DNA as the source of genetic information: The Hershey-Chase Experiment (1952)
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10/19/09 3 DNA as the source of genetic information: The Hershey-Chase Experiment (1952) 35 S to label protein 32 P to label DNA Concept check • Could Hershey and Chase have used a radioactive isotope of carbon instead of 32 P? Why or why not? RNA as genetic material
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10/19/09 4 Historical experiments Hershey and Chase: DNA is the genetic material in viruses (2nd demonstration) Griffith: transforming principle Avery et al: transforming principle DNA is the genetic material in bacteria RNA is genetic material (in some viruses) Primary structure of DNA • Nucleotide – Ribose or Deoxyribose sugar – Nitrogenous base – Phosphate group A nucleotide contains either a ribose or deoxyribose sugar. Additional oxygen, recognized by different enzymes, more reactive Forms covalent bond with base Forms bond with phosphate group
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10/19/09 5 A nucleotide contains either a purine or pyrimidine base A nucleotide contains a phosphate group. Structures of the four DNA nucleotides:
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10/19/09 6 Thought question: DNA molecules of different sizes are often separated with the use of a technique called electrophoresis. With this technique, DNA molecules are placed in a gel, an electrical current is applied to the gel, and the DNA molecules migrate toward the positive (+) pole of the current. What aspect of its structure causes a DNA molecule to migrate toward the positive pole? Watson and Crick’s Discovery Photograph from Maurice Wilkins X-ray diffraction, structural chemistry, modeling Polynucleotide strands: phosphodiester bonds join 5’ - phosphate group of one nucleotide join to the 3’ - carbon group of the next nucleotide. This results in a direction, or polarity, of the strand. 5- end, 3- end.
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7 Base pairing in DNA
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This note was uploaded on 10/03/2010 for the course RUT 146:356 taught by Professor Gol during the Spring '10 term at Rutgers.

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Genetics380_DNA2009s - Topic DNA structure replication and repair Reading.1-12.3 and 18.2-18.4 DNA as the source of genetic information The

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