how the form and function of dna relate

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:

• 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

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 moleculeForm Function