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The technique first developed
by Maurice Wilkins and Rosalin Franklin and used by James Watson
and Franics Crick to determine the double helix structure of DNA is known as X-ray crystallography. X-rays are synchronized so
that the crests and troughs are in identical locations.
These rays are then bounced off of the DNA molecule to
form an image on photographic film. X-rays are used due
to their low wavelength, between 0.05 angstrom and several hundred
angstroms. The wavelength of normal light is
hundreds of times longer, making the offset caused by the
molecule so small that it is of no use. As the X-rays
impact the DNA, they are reflected at different angles
and at different times in their cycles (because the
distance traveled is different for each wave). This
causes a pattern to form. However, when only one molecule
is used, the image is very faint. To enhance and amplify
it the image, the molecules must be arranged in order, as
in a crystal. DNA is arranged in crystal form by turning
it into a gel. A small object can then be inserted into  the mixture. When twisted,
the object will pull out a strand of several DNA
molecules, all in order. This strand can then undergo
X-ray crystallography, and produce a much stronger image.
X-ray
crystallography image courtesy of the British Biophysical Society.
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1998 by team 24355 and Kayotic Development.
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