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…
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
__________?_____________ .
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:
% of Nitrogenous bases
A
Octopus 33.2
Chicken 28.0
Rat
?
Human 29.3
• Conclusion?
http://www.dnalc.org/resources/3d/21-chargaff-ratios.html
G
17.6
21.5
21.9
20.7
C
?
21.5
21.9
20.0
T
31.6
?
28.6
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): 2 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.”
Where does DNA live?
What is happening here?
• 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)
List the ways form and function of DNA
are linked
DNA molecule
Form
Function