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DNA

DNA. SC STANDARD B-4: THE STUDENT WILL DEMONSTRATE AN UNDERSTANDING OF THE MOLECULAR BASIS OF GENETICS. Cornell Notes. Topic: DNA EQ: How does the overall structure of DNA explain the mechanism of inheritance?. History. Griffith’s Experiment. 1928: Griffith Transformation :

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DNA

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  1. DNA SC STANDARD B-4: THE STUDENT WILL DEMONSTRATE AN UNDERSTANDING OF THE MOLECULAR BASIS OF GENETICS

  2. Cornell Notes Topic: DNA EQ: How does the overall structure of DNA explain the mechanism of inheritance?

  3. History Griffith’s Experiment • 1928: Griffith • Transformation : • Process by which 1 strain of bacteria is changed into a 2nd strain after being in the presence of the 2nd strain

  4. DNA • Avery: 1944 • Identified transforming agent as DNA

  5. Bacteriophages infect bacteria and transfer their genetic material to the bacteria’s DNA. These experiments proved it was the genetic material not the protein that “transformed” the bacteria. Hershey-Chase Experiment

  6. DNA • 5-carbon sugar: deoxyribose • Phosphate group • Nitrogenous Base • Purines • Adenine • Guanine • Pyrimidines • Cytosine • Thymine Parts of DNA

  7. In same sample of DNA: • cytosine = guanine • [ C ] = [ G ] • adenine = thymine • [ A ] = [ T ] Chargaff’s Rules

  8. Rosalind Franklin • studied DNA using x-ray diffraction • The pattern on the left gave some important clues as to the structure of DNA • shaped in a helix • nitrogenous bases in center X-RAY EVIDENCE

  9. Watson & Crick • Built 3-D models trying to find a structure that explained everything they knew DNA could do • When they saw Franklin’s x-rays the shape became clear to them THE DOUBLE HELIX

  10. DNA Had to be able to do 3 things: carry information from 1 generation to next use the information to produce traits be easily copied

  11. THE DOUBLE HELIX

  12. DOUBLE HELIX TWISTED LADDER WITH RUNGS OF LADDER MADE UP OF THE NITROGENOUS BASES HELD TOGETHER BY HYDROGEN BONDS

  13. DOUBLE HELIX BASE PAIRING EXPLAINED CHARGAFF’S RULES SINCE ADENINE ALWAYS PAIRED WITH THYMINE & GUANINE ALWAYS PAIRED WITH CYTOSINE

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