More to Explore 197
cally pass this information to a new cell, a new organism, and a new generation. To answer
that question, someone had to first figure out what this giant DNA molecule looked like.
At Cambridge, Crick teamed with American biologist James Watson. The two agreed
to pool their efforts to construct a model of the DNA molecule while they pursued their separate studies and thesis research.
By 1951 bits and pieces of information about the DNA molecule were emerging from
across the globe. Erwin Chargaff discovered that a definite ratio of nucleotide sequences
could be detected in the DNA bases, suggesting a paired relationship. Oswald Avery conducted experiments on bacteria DNA showing that DNA carried genetic information. Linus
Pauling conceptualized the alpha helix configuration for certain chains of proteins.
Crick and Watson attempted to combine these separate clues into a single physical
structure. Using bits of wire, colored beads, sheet metal, and cardboard cutouts, Crick and
Watson hung possible spiral models across their shared office. They correctly surmised that
a linking chain of sugar and phosphate formed the backbone of the DNA spiral. They correctly linked base pairs of peptides. Still the model did not fit with available atomic data.
Also at Cambridge, but independent of Crick and Watson’s efforts, Rosalind Franklin
used X-ray crystallography to create two-dimensional images of the DNA molecule. In
mid-January 1953, Rosalind had redesigned the X-ray cameras she used. X-ray film from
these cameras showed the now-famous “X” shape that suggested a helix shape for the DNA
molecule.
Tipped off that Franklin had new information, Crick stole one of Rosalind’s X-shaped
X-rays. This stolen insight finally put Crick and Watson ahead in the race to solve the structure of DNA. By mid-February they had constructed the first complete physical model of a
DNA molecule, using the now-familiar double helix shape, like two intertwined spiral
chains.
Fun Facts: If you straightened each strand of DNA from each cell in
your body and lined them end-to-end, you’d have about nine million kilometers of DNA. That’s enough to reach to the moon and back 13 times!
More to Explore
Crick, Francis. Life Itself: Its Origins and Nature. New York: Simon & Schuster,
1981.
———. Of Molecules and Men. Washington, DC: Washington University Press,
1966.
Judson, Horace. The Eighth Day of Creation: Makers of the Revolution in Biology.
London: S & S Trade Books, 1999.
Maitland, Edey, and Donald Johanson. BLUEPRINTS: Solving the Mystery of Evolution. New York: Penguin Books, 1996.
More, Ruth. The Coil of Life: The Story of the Great Discoveries of the Life Sciences.
New York: Knopf, 1991.