dna
DESCRIPTION
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 : - PowerPoint PPT PresentationTRANSCRIPT
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DNASC STANDARD B-4: THE STUDENT WILL DEMONSTRATE AN UNDERSTANDING OF THE MOLECULAR BASIS OF GENETICS
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Cornell NotesTopic: DNA
EQ: How does the overall structure of DNA explain the mechanism of inheritance?
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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
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DNA
Avery: 1944◦Identified transforming agent as DNA
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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.
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Parts of DNA
DNA
1. 5-carbon sugar: deoxyribose
2. Phosphate group3. Nitrogenous Base
1. Purines1. Adenine2. Guanine
2. Pyrimidines1. Cytosine2. Thymine
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Chargaff’s Rules
In same sample of DNA:
cytosine = guanine ◦[ C ] = [ G ]
adenine = thymine◦[ A ] = [ T ]
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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
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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
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DNAHad to be able to do 3 things:1. carry
information from 1 generation to next
2. use the information to produce traits
3. be easily copied
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THE DOUBLE HELIX
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DOUBLE HELIXTWISTED LADDER WITH RUNGS OF LADDER MADE UP OF THE NITROGENOUS BASES HELD TOGETHER BY HYDROGEN BONDS
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DOUBLE HELIXBASE PAIRING EXPLAINED CHARGAFF’S RULES SINCE ADENINE ALWAYS PAIRED WITH THYMINE & GUANINE ALWAYS PAIRED WITH CYTOSINE