A transgenic crop plant contains a gene or genes which have been
artificially inserted instead of the plant acquiring them through
pollination. The inserted gene sequence (known as the transgene)
from another unrelated plant, or from a completely different species:
transgenic Bt corn, for example, which produces its own insecticide,
contains a gene from a bacterium. Plants containing transgenes are often
called genetically modified or GM crops, although in reality
have been genetically modified from their original wild state by
domestication, selection and controlled breeding over long periods of
time. On this web site we will use the term transgenic to describe
a crop plant which has transgenes inserted.
Image:Results of insect
infestation on Bt (right) and non-Bt (left) cotton bolls.
Why Make Transgenic Crop Plants?
A plant breeder tries to assemble a combination of genes in a crop
plant which will make it as useful and productive as possible. Depending
on where and for what purpose the plant is grown, desirable genes may
provide features such as higher yield or improved quality, pest or disease
resistance, or tolerance to heat, cold and drought. Combining the best
genes in one plant is a long and difficult process, especially as
traditional plant breeding has been limited to artificially crossing
plants within the same species or with closely related species to bring
different genes together. For example, a gene for protein in soybean could
not be transferred to a completely different crop such as corn using
traditional techniques. Transgenic technology enables plant breeders to
bring together in one plant useful genes from a wide range of living
sources, not just from within the crop species or from closely related
plants. This technology provides the means for identifying and isolating
genes controlling specific characteristics in one kind of organism, and
for moving copies of those genes into another quite different organism,
which will then also have those characteristics. This powerful tool
enables plant breeders to do what they have always done - generate more
useful and productive crop varieties containing new combinations of genes
- but it expands the possibilities beyond the limitations imposed by
traditional cross-pollination and selection techniques.
Image: A plant breeder cross-pollinating corn plants.
Page last updated : March 11, 2004
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