How the form and function of DNA relate.
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Transcript of How the form and function of DNA relate.
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To pass on your genes ?
argue for or against, with evidence
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Your task: Design a molecule that can…
• Self-replicate• Make something else from simple building
blocks
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How the form and function of
DNA relate.
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Before knowledge of DNA, how did we
explain how traits are passed on from parent
to offspring?
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a lesson in progress…
• Frederick Griffith (British, 1928):– Wanted to find out how/why certain bacteria
make you sick
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What was Griffith’s grand conclusion?
• Griffith performed what he called transformation, a term still used today
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Step 2…
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Step 2…
• Oswald Avery (1944, Canadian) used enzymes to break down the cell’s components (lipids, nucleic acids, proteins, carbohydrates) of the bacteria cells in Griffith’s experiment
• Results: Griffith’s process did not work when __________?_____________ .
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Hershey–Chase experiment: a verification of Avery
Alfred Hershey and Martha Chase (American, 1952)
– Conclusion?
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Rosalind Franklin (50’s British) and the
first image of DNA
• Used x-ray diffraction to get this image• What hints about the structure can be gained
from this?
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Chargaff’s Rules and the first insight into how DNA works
• American biochemist Erwin Chargaff isolated molecules from DNA in the following proportions:
• Conclusion?http://www.dnalc.org/resources/3d/21-chargaff-ratios.html
% of Nitrogenous bases
A G C TOctopus 33.2 17.6 ? 31.6Chicken 28.0 21.5 21.5 ?Rat ? 21.9 21.9 28.6Human 29.3 20.7 20.0 30.0
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The grand conclusion
• James Watson (British physicist) and Francis Crick (American biologist) 1953:
• DNA is a….DOUBLE HELIX
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• A closer look
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DNA’s specifications
• Width: 2 nanometer (nm), or 2 billionths of a meter
• Length (per cell): 2 m– How does it all fit in one cell?
• How much total length of DNA in one human?– How far is that?
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Where does DNA live?
Click on the following link for a “journey into DNA.”
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Where does DNA live?
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What is happening here?
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• Watch the replication of DNA:– http://www.hhmi.org/biointeractive/dna/animations.html (technical)– http://www.teachersdomain.org/asset/tdc02_vid_dnaanimation/– http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html (replication
workshop, Shockwave activity)– http://www.youtube.com/watch?v=OnuspQG0Jd0&safe=active
(technical, but good)
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List the ways form and function of DNA are linked
DNA moleculeForm Function