New agony over breast cancer
By Rita Rubin
Plaque-reducing protein shows promise
By Steve Sternberg
Amgen thinks small to grow
By Matt Krantz
Bacteria-powered battery runs on a sweet tooth
By Elizabeth Weise
Bio-food fight centers on Africa
By Elizabeth Weise
Discussion Questions and Additional Resources
Biotechnology is a way of making commercial products using living
cells. Yeast have been used to make bread, wine, and beer for centuries.
Without refrigeration, fermented foods last longer than fresh food.
For example, cheese and yogurt can be kept longer than milk because
of the acids and antibiotics produced by bacteria during fermentation.
Advances in Biology during the latter part of the 20th century led
to improved understanding of the relationship between specific microbes
and their products. When World War I interfered with picking the
Italian lemon crop, biologists turned to Aspergillus fungus to produce
citric acid for food flavoring and preservation. During World War
II, acetone for gunpowder and butyric acid for synthetic rubber
were produced by Clostridium bacteria. Following World War II, large
scale production of penicillin and streptomycin was accomplished
by growing Penicillium fungus and Streptomyces bacteria in large
Techniques quickly became more sophisticated as scientists learned
to mutate wild Penicillium to make the fungus produce more penicillin.
Until the 1980s, products made by living cells were all naturally
made by the cells; the role of scientists was to find the appropriate
cell and develop a method for large-scale cultivation.
For years people have genetically modified plants and animals by
selective breeding. This technique is hit-or-miss because one doesn't
always get the desired character such as more milk or sweeter fruit
from mating two parents. In 1980, Paul Berg showed that animal genes
can be attached to bacterial DNA. The resulting hybrid was the first
example of recombinant DNA. When recombinant DNA is inserted into
a cell, it can be used to make large quantities of the desired protein.
The applications of genetic engineering are increasing each year.
Recombinant DNA techniques have been used to make bacteria and fungi
that produce a number of natural proteins, vaccines, and enzymes.
Such substances have great potential for medical use and because
living cells make them, production doesn't involve expensive and
dangerous chemicals or high temperature or pressure, and the cells
don't produce toxic wastes. For example, some individuals do not
produce enough human growth hormone, consequently their growth is
stunted. Traditionally, the hormone was extracted from cadavers.
However, diseases can be transmitted with the cadaveric hormone.
Human growth hormone produced by genetically modified bacteria is
pure and cost-effective.
Recombinant DNA techniques have also been applied to agriculture.
Plants have been genetically modified to resist insect damage and
herbicides and to prolong shelf life. And genetically modified bacteria
have been used to prevent frost damage to crops.
The recently completed Human Genome Project was a massive undertaking
to sequence the three billion nucleotide pairs in human DNA. The
next step is to identify the genes in these three billion nucleotide
pairs and identify the proteins they produce. The process is already
providing invaluable information regarding the abnormal proteins
produced by some forms of genes. This can lead to treatments to
replace or change the abnormal protein.
Several recent articles in USA Today describe how biotechnology
is affecting human health.