Download Experiment

Monday
3-8-2010
NOTES:
DNA Experiments & Structure
(1) Griffith’s Experiment:
• Question: What about a “disease” kills animals?
• Experiment:
– Injected some mice w/dead bacteria
– Injected some mice w/dead disease bacteria,
and living normal bacteria
• Results:
– Mice w/only dead bacteria  No Disease
– Mice w/Mixture  Disease
– “Disease” carried in some molecule, which was
passed on to the living-normal bacteria!
http://www.quia.com/files/quia/users/hlrbiology/An
imations/08_DNA_and_Proteins/Griffith_Mouse
_Experiment.swf
(2) Hershey-Chase Experiment:
• Question: Does DNA or Protein contain genetic
information?
• Experiment:
– Dyed the DNA, and the protein in viruses.
– Infected bacterial cells with the viruses.
• Results:
– DNA ended up inside the bacteria, and made
more viruses.
– Protein stayed outside the bacteria.
– DNA contains genetic instructions, not protein!
• http://highered.mcgraw-hill.com/olc/dl/120076/bio21.swf
(3) Wilkins & Franklin’s Experiment:
• Question: What is the overall shape of
DNA?
• Experiment:
– Shot X-rays at DNA crystals
– Recorded the ray-pattern
• Results:
– Produced an X-Ray diffraction photograph.
– Saw an uneven, X shape.
– DNA is a double helix with minor and major
grooves!
(4) Watson & Crick’s Experiment:
• Question: What is the chemical structure of DNA?
• Experiment:
– Pieced the DNA compounds together like a puzzle.
• Results:
–
–
–
–
Phosphate and Sugar alternate on the outside of DNA.
Nitrogenous Bases are inside the helix.
Adenine forms 2 hydrogen bonds w/Thymine.
Guanine forms 3 hydrogen bonds w/Cytosine.
(5) Nucleotide:
• Nucleotide: The monomer of a nucleic acid
(like DNA).
• Made Of:
– 1-Phosphate
– 1-Sugar
– 1-Nitrogenous Base
(6) DNA Structure:
• Double Stranded
• Double Helix
• Anti-parallel strands
• DNA Nucleotides:
– Phosphate
– Deoxyribose Sugar
– Nitrogenous Bases:
•
•
•
•
A = Adenine
T = Thymine
G = Guanine
C = Cytosine
(7) Anti-Parallel Strands
Anti = Opposite
•
Strands are flip-flopped from one another
•
One Strand’s 3’ End, matches the other’s 5’
End!
(8) Chargaff’s Rule:
• Adenine ---- Thymine
– %A = %T
• Guanine ---- Cytosine
– %G = %C
• (A+T) + (G+C) = 100%
– Use this to determine percentage of types of
bases.