Scientists have done this with the bacterium Bacillus
thuringiensis, or Bt for short. Bt, which is found naturally
in soil and on the leaves of many plants, is toxic to many plant
pests. The genes that give it that toxicity were first put into
potatoes in 1997. Now many vegetables grown commercially have
the Bt genes in them.
This gene-adding process is called “genetic engineering”
(GE). GE is one form of what’s called “genetic modification”
(GM). Though GE and GM are related, they are not the same. “Genetically
modified” refers to any plant (or other organism) whose DNA
has been manipulated by humans. This could happen through artificial
selection and hybridization or through engineering. “Genetically
engineered” refers specifically to one or more extra genes
that have been inserted into a plant’s genome from an organism
it can’t mingle genes with via sexual reproduction. The products
of such engineering feats— like Bt tomatoes—are called
Intuitively, GE doesn’t seem like a very “natural” process.
After all, genes in nature don’t cross so many boundaries.
But the line between natural and unnatural may be grayer than you
In the wild, most plants (actually, most living things) share
genes only with members of their own or very closely related species
living in nearby environments. Hybridization allows plant breeders
to go beyond these limitations that exist in nature. Suppose a
wild tomato exists that seems particularly resistant to cold. A
breeder can cross this plant with one that produces store-bought
tomatoes in order to impart these useful ancestral genes. The resulting
tomatoes may look and taste like the ones we’re familiar
with, and their DNA doesn’t contain any “nontomato” genes.
But this cross isn’t natural: these two plants would never
have found each other in the wild. In fact, the grocer’s
tomato doesn’t even exist in nature. It’s the product
of hundreds of similar hybridizations.
The main difference between a hybridized tomato and a transgenic
one is that the latter has additional bits of DNA that originally
came from another species. It has an altered genome. Critics of
genetic engineering have argued that this process may have unintended
consequences: They are concerned that seeds from GE plants could
carry their genetic alterations into the environment and the food
supply, or that untested GE products may pose health risks for
consumers. Supporters of genetic engineering counter that the benefits
of GE—plants with added nutrition, higher yields, or the
ability to produce pesticides or drugs—outweigh the risks,
and that a world with rapidly increasing population can’t
be fed without them.
Different countries have adopted different policies toward the
growing, selling, and labeling of genetically engineered foods.
For example, GE ingredients in packaged foods have to be identified
as such in Europe, but not in the United States. Until March 2005,
farmers in Brazil were not allowed to grow GE crops, while farmers
in the United States have long been encouraged to do so. In addition,
the companies that develop genetically-engineered crop plants claim
ownership of the seeds and any plants they produce as offspring
for several generations. This has met with resistance from farmers
around the world, some of whom have had pollen from GE plants blown
or carried into their fields, and others in developing countries
who would like the benefits of genetic engineering without being
dependent on seed producers for their seed supply.
As a backyard gardener, you’re not likely to be planting
any transgenics. These engineered plants have been developed for
agriculture. They are patented, and the companies that sell them
would make you aware of that when you buy them. That doesn’t
mean, however, that the plants you grow in your garden are
the products of completely natural processes. There’s manipulations
everywhere out there.
Links presenting various views on transgenics, from the Action
Bioscience Web site, produced by the American Institutes of Biological
Biotechnology and the Green Revolution: An Interview with
Borlaugh has been involved in crop improvement since the 1940s, and won the
Nobel Peace prize in 1970 for his work. He is an staunch advocator of genetic
engineering to increase crop yields and provide more food in developing nations.
The Ecological Impacts of Agricultural Biotechnology
The Debate Over Genetically Modified Foods
By Miguel A. Altieri
Altieri teaches agroecology at the University of California at
Berkeley, and also works on sustainable agriculture issues for
the United Nations. He has been outspoken about his concerns regarding
the ecological risks of plant biotechnology.
By Kerryn Sakko
This article describes some of the differences between breeding
and genetically engineering crops, and presents arguments on both
sides of the issue. Written by an undergraduate student from Australia
who represented her country at the 2004 Youth Science Festival
in Singapore, sponsored by Asia-Pacific Economic Cooperation Forum.
Other Web site resources:
How do you make a transgenic plant?
Produced on behalf of the food and drink industry in the
United Kingdom, this site presents many perspectives on questions
such as “Who owns GM technology” and “What about
Through animations, illustrations, and text, this page gives background
on DNA and describes how scientists move genes from one organism