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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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slide1

DNA

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

cornell notes
Cornell Notes

Topic: DNA

EQ: How does the overall structure of DNA explain the mechanism of inheritance?

slide3
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
slide4
DNA
  • Avery: 1944
    • Identified transforming agent as DNA
hershey chase experiment
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
parts of dna
DNA
  • 5-carbon sugar: deoxyribose
  • Phosphate group
  • Nitrogenous Base
    • Purines
      • Adenine
      • Guanine
    • Pyrimidines
      • Cytosine
      • Thymine
Parts of DNA
chargaff s rules
In same sample of DNA:
  • cytosine = guanine
    • [ C ] = [ G ]
  • adenine = thymine
    • [ A ] = [ T ]
Chargaff’s Rules
x ray evidence
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
the double helix
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
slide10
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

double helix
DOUBLE HELIX

TWISTED LADDER WITH RUNGS OF LADDER MADE UP OF THE NITROGENOUS BASES HELD TOGETHER BY HYDROGEN BONDS

double helix1
DOUBLE HELIX

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