What Is Biotechnology? - Biotechnology and Your Health: Pharmaceutical Applications - page 4

in different parts of the body. The production of different proteins
by cells is what gives each cell its properties and the organism as
a whole its traits. The human body produces more than 70,000
different proteins; a single liver cell has approximately 10,000 dif-
ferent proteins. Within every cell of every organism, the integrated,
finely orchestrated functioning of these proteins, both separate and
together, is central to life.
What Is a Gene?
To figure out how genes work and how they direct the production
of specific proteins that allow organisms to inherit traits, scientists
started with the fact that chromosomes were known to be made up
of protein and DNA. A series of experiments using bacteria and
viruses that infect bacteria established that DNA, not protein, was
the basic genetic material. Scientists figured out how DNA “worked”
as the genetic material, how it was copied when a cell divided into
two identical cells, and how DNA determined traits—that is, deter-
mined the sequence of amino acids in each protein that allow
different traits to be expressed.
DNA molecules are chains of four bases : adenosine (A), cytosine
(C), guanine (G), and thymine (T). Each of these bases is slightly
different from the others in its chemical makeup. Figuring out
the structure of DNA provided the clues to how DNA worked to
transmit genetic information (Figure 1.1).
UNLOCKING THE SECRET OF DNA
In 1962, James Watson, Francis Crick, and Maurice Wilkins won the
Nobel Prize in Physiology or Medicine for their discovery that the
structure of DNA is a double helix . This double helix is made up of
two chains of DNA bound to each other by the ability of each A base
to form a weak chemical bond to a T base and each C to a G. The
bases only paired with their base partners, so that where one strand
had a T, the other had an A, and where one had a C, the other had