Bt Crop Specificity

Bt plants are more specific than other insecticidal sprays used (DeMaagd, R. A. and et al., 1999). Bt plants are more specific because they produce only one Bt toxin. Insecticidal sprays contain several different Bt toxins. Each toxin affects a specific order of insects-called target insects (DeMaagd, R. A. and et al. , 1999). Therefore the insecticidal sprays affect numerous orders of insects. This specificity makes Bt plants safer than insecticidal sprays (DeMaagd, R. A. and et al. , 1999). Non-target insects, also called beneficial insects, are insects that the Bt plant is not supposed to affect (Wu, K., and Guo, Y., 2003). Bt plants are tested against non-target insects to insure their specificity prior to being introduced into the environment (DeMaagd,
R. A. and et al. , 1999).

Colorado Potato Beetle	European corn borer

permission pending from European Corn Borer, 2000

Different Bt crystal proteins are specific to different receptors in insects' gut cells. Bt toxicity depends on distinguishing among receptors on intestinal cells. Gut damage occurs when the Bt crystal protein binds to the receptors on the intestinal cells. (See Environmental Disturbance for more info on Bt toxin mechanisms.) Each insect species possesses different types of receptors that will match only certain toxin proteins (Bacillus thuringiensis ). Therefore, a given toxin works for only certain insects that possess the correct receptor. Bt crops are not harmful to humans, because humans do not have receptors for Bt proteins. Other vertebrates do not have these receptors either ( Bacillus thuringiensis ).

Bt Crystals
permission pending from P. Grochulski

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as part of an undergraduate assignment at Davidson College.

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