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DNA . Hot Science . Gallery of Genetic Modifications
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Bt Corn

Bt corn has been engineered to include a gene from Bacillus thuringeiensis, a bacterium that lives in the soil and naturally produces a toxin that functions as a pesticide. The Bt strain of corn is able to produce this pesticide in its pollen. The toxin is particularly effective in defending crops from Lepidopteran caterpillar pests, in particular the European corn borer. The Bt technology has also been employed for use with cotton crops.

Bt crops have proven popular with farmers, but in May 1999 there were concerns over the technology when a study released by the science journal NATURE suggested the toxin in the corn pollen may also be detrimental to the larvae of monarch butterflies -- a kind of Lepidopteran insect. A subsequent study confirmed the results of the NATURE research, yet in 2001, the results of several additional studies were published in the PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCE. The new research suggested that, in the field, the actual impact of Bt corn on monarch butterflies was negligible.

Meanwhile, another fear over genetically engineered Bt crops was raised in September 2000, when StarLink corn, a brand of Bt corn designed for stock feed and not approved for human consumption, was found in Taco Bell taco shells distributed by the Kraft corporation. Kraft voluntarily recalled all of its taco shells that may have contained StarLink corn. Yet in the following weeks, the StarLink corn was detected in many other food products, some even outside the U.S. It became apparent that farmers had sold an unapproved strand of modified corn, and subsequent interviews with the growers suggested they may not have been clearly instructed not to sell the StarLink corn for human use. Proponents of genetic engineering have argued that the StarLink incident is evidence of the effective controls in place to monitor the modified crops entering our food supply. Today, corn buyers routinely screen for the presence of StarLink corn.

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