Embed Size (px)
Citation preview
To pass on your genes ?
argue for or against, with evidence
Your task: Design a molecule that can…
• Self-replicate• Make something else from simple building
blocks
How the form and function of
DNA relate.
Before knowledge of DNA, how did we
explain how traits are passed on from parent
to offspring?
a lesson in progress…
• Frederick Griffith (British, 1928):– Wanted to find out how/why certain bacteria
make you sick
What was Griffith’s grand conclusion?
• Griffith performed what he called transformation, a term still used today
Step 2…
• Oswald Avery (1944, Canadian) used enzymes to break down the primary components (lipids, nucleic acids, proteins, carbohydrates) of the bacteria cells in Griffith’s experiment to determine which component was exchanging information.– Results: Griffith’s process did not work when Avery
used enzymes to breakdown the nucleic acid of the deadly bacteria
Hershey–Chase experiment: a verification of Avery
Alfred Hershey and Martha Chase (American, 1952)
– Conclusion?
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?
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 17.6 31.6Chicken 28.0 22.0 21.6 28.4Rat 28.6 21.4 20.5 28.4Human 29.3 20.7 20.0 30.0
The grand conclusion
• James Watson (British physicist) and Francis Crick (American biologist) 1953:
• DNA is a….DOUBLE HELIX
• A closer look
DNA’s specifications
• Width: 2 nanometer (nm), or 2 billionths of a meter
• Length (per cell): 1 m– How does it all fit in one cell?
• How much total length of DNA in one human?– How far is that?
Where does DNA live?• Click on the following link for a “journey into DNA.”• http://www.pbs.org/wgbh/nova/genome/dna.html#
• List the ways form and function fulfilled.
• Watch the replication of DNA:– http://www.hhmi.org/biointeractive/dna/animati
ons.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)
