What Is the Bt(Bacillus thuringiensis) Gene?

 What Is the Bt(Bacillus thuringiensis) Gene?

Bacillus thuringiensis, or Bt, is a type of bacterium found in soil. Bt bacteria produce protein crystals known to be toxic to several varieties of insect larvae, including moths, beetles, mosquitoes, black flies, nematodes and flatworms. The Bt gene is a small stretch of DNA from the Bt chromosome that codes for the production of these protein crystals. Davidson College states that both Bt bacteria and the Bt gene products are used as insecticides in the U.S., Canada, Argentina, South Africa and parts of Europe.

History:

 Bt bacteria were discovered in 1901 in Japan, and were brought to the U.S. in 1958 for agricultural use. Initially, the bacteria were grown and harvested to be used as crop sprays and dusts, according to Davidson College. As the field of genetic engineering evolved and the Bt gene was identified and isolated, it became one of the first genes to be inserted directly into the hereditary structure or genome of plant crops, creating genetically modified Bt crops. In doing so, the plants themselves were able to produce the toxic protein crystals and thus become resistant to Bt affected insects without the need for spraying.

Uses:

Today the Bt gene has been incorporated into a variety of cash crops grown and sold around the globe, including corn, potatoes, broccoli, cauliflower, cotton and tobacco. Whole Bt bacteria are still dusted in U.S. forests to control spruce budworms and gypsy moths, according to Iowa State University. Bt is also used in common household insecticide sprays intended for garden use.

Benefits:

Bt is washed away from plants with water or rain, and it is broken down by sunlight. These properties convey an environmental benefit. However, as the Bt must be eaten by insects to be effective, this trait makes Bt a less potent insecticide than some synthetics which kill on contact. By genetically engineering crops to contain the Bt gene and be constantly producing their own Bt toxin, the plant will be insect resistant regardless of weather patterns. Bt crops can also kill insects even after they have invaded the plant tissues, as reported by Iowa State University.

Safety

Both Bt crops and commercially produced Bt insecticides are classified as "Generally Regarded as Safe" (GRAS) by the Environmental Protection Agency. The protein crystal which is toxic to insects is safe for human consumption, as humans lack the digestive enzyme required to convert the protein to its toxic form, according to Davidson College. Studies of Bt's effects on animals have produced contradictory results, and it is lethal to Monarch butterflies.

Considerations

One cost of producing Bt crops is that insect resistance will still occur, likely at a higher rate than it would in non-Bt crops. Bt will kill most of a given species of insect, but never all of them. Of those that survive, a high percentage of them will be naturally Bt resistant, becoming the parents of future generations. A second issue with genetically modified crops involves gene flow, the unintentional transfer of genes from one plant species to another, according to Davidson College. This may occur through pollination of Bt crops grown in close geographic proximity to other crops, thereby introducing Bt genes into other plants.
  
Source:http://www.ehow.com/about_7238414_bt-gene_.html