Page 14 - An Identity Crisis

Forensic DNA
Technology

ach individual, with the exception of different bases. Watson and Crick also knew that
identical twins, has a unique array of genetic the base Adenine (A) and the base Thymine (T)
Einformation within their deoxyribonucleic were present in equal amounts, while the base
acid (DNA). This information is identical in each Cytosine (C) and the base Guanine (G) were
nucleated cell in the body and acts as a “genetic present in equal amounts. In addition, Watson
blueprint”, containing the instructions to build and Crick had an X-ray picture of the crystalline
living organisms. This blueprint specifies physical structure of DNA by another scientist, Rosalyn
characteristics such as eye color, height, and blood Franklin, which showed that DNA has a helical
type. structure, like a corkscrew. Watson and Crick built
a DNA model with two strands of chemically linked
In the early 1950s, two scientists, James Watson nucleotides that twisted around each other to form
and Francis Crick, determined the 3-dimensional a ladder-like structure called a double helix, and
structure of the DNA molecule. Watson and Crick this model is still used today. A negatively charged
knew that DNA was made up of four building phosphate/sugar backbone formed the legs of the
blocks, called nucleotides, and that each nucleotide ladder, pairs of nucleotides, one on either side of
contained a sugar, a phosphate, and one of four the ladder, faced the center of the helix and linked

14 THE MYSTERY OF LYLE AND LOUISE