Biology

Why BT-corn is developed
Corn is an important food for humans and it is used as a source for industrial raw materials. But, it is mainly used to feed the animals by approximately two-thirds of population. There are many uses of corn as there are many different types available such as popcorn, sweet corn, field corn etc.

Because of its importance economically, corn has been widely and intensively bred to manufacture high yielding hybrids that are opposed to pests, diseases, and environmental stresses, suitable for changing climatic conditions, and simple to produce.

Even with the rewards of new hybrids, growers face a variety of challenges in sustaining levels of production and, simultaneously, preserving the fertility of soil and structure, and caring the environment.

Corn yields can be decreased by weeds, pests, weather damage, and a broad range of bacteria and fungi. Many insects damage the corn yields, but one of the most destruction is corn borer. Corn borer is so called because the moths larvae tunnel into the plant and eat as they go. It is estimated that every year, forty million tons of corn never arrive at the market due to the damage by corn borer. Biological control techniques and chemical insecticides exist to manage epidemic of corn borer, but the infestation nature makes it hard and costly to deal with.

This is the reason why BT corn, a genetically modified corn, was introduced in 1996, with in-built resistance to the corn borer (Syngenta, 2003).What is BtBT (Bacillus Thuringiensis) is a naturally occurring soil-borne bacterium that is found globally. The exclusive characteristic of this bacterium is its production of crystal like proteins that kill selectively particular groups of insects. These crystal proteins or Cry proteins are insect stomach poisons that should be eaten for killing the insects. Once these proteins are eaten, the insects own digestive enzymes stimulate the proteins toxic form. The Cry proteins attach to the particular receptors on the lining of the intestine and rupture the cells. Within two hours of the first bite, insects stop feeding and if sufficient toxic is eaten, they die within two to three days.

How Bt-corn was madePlant geneticists made Bt corn introducing selected exotic DNA into the corn plants DNA. DNA, a genetic material, controls the expression of animals or plants traits. The Bt gene, which is modified for improved expression in corn, create the crystal proteins that are toxic to some caterpillars such as the European corn borer. Promoters decide where the toxin should be put in the plant. Varieties that put across the toxin in kernels, pith, and silks tend to present longer season safety than varieties that put across only in the green tissue and pollen of the plant (Wisconsin College of Agricultural and Life Sciences).

How was the gene isolated and used
To change a plant into genetically modified plant, the gene that develops a genetic characteristic of interest is recognized and separated from the remaining genetic material from a donor organism. Most organisms consist of thousands of genes, and a single gene signifies only a small part of the complete genetic makeup of an organism.

The donor organism can be a fungus, bacterium or another plant. In the case of BT-corn, the naturally occurring soil bacterium, Bacillus Thuringiensis (BT) is the donor organism. The gene of interest produces a protein, BT delta endotoxin, that kills Lepidoptera larvae, mainly, European corn borer. Cultivators use BT-corn as a substitute to spraying insecticides for controlling the European and Southwestern corn borer.The BT delta endotoxin was chosen because it is very much efficient at managing the Lepidoptera larvae, caterpillars. The protein is very choosy, normally not hurting insects (such as bees, beetles, wasps, and flies).

This protein is also believed to be harmless for humans, fish, birds, other mammals and insecticides.For killing a susceptible insect, a plant part that includes Bt protein should be ingested. Within a few minutes, the protein attaches to the gut wall and the insect ends feeding. The gut wall breaks down within hours and the usual gut bacteria attack the body cavity. The bacteria multiply in the blood leading to septicemia and the insect dies. How was the gene infused into the corn plant After recognizing the gene that develops a genetic trait of interest, trait should be added to the crop plant. For adding a trait to the crop plant, the gene should be placed along with added genetic material. A promoter sequence is present in the additional genetic material that decides how a new trait is put across in the plant. For example, the promoter sequence may cause the protein to be put across in some parts of the plants or during a specific time period. Marker genes are also present that lets plant breeders to simply decide which plants have been changed (The University of Kentucky College of Agriculture, 1999). Benefits with Bt-cornBt corn decreases the necessity for pesticides, and while the major advantage comes mostly during a serious corn borer infestation, an erratic occasion, a secondary advantage is that helpful insects fare a lot better under these situations. Growers who take on genetically modified crops benefit much in tough periods. In fact, virus and insect resistant traits have saved already a number of industries. According to the latest review of International Council for Science (ICSU), corn crops that are disease resistant may have lower mycotoxin levels, which are possibly carcinogenic compounds to human beings. Mycotoxins occur from the activity of fungus in insect-infested corn yields. With less insect holes in tissues of plant, related fungi are not able to attack and create toxins (Gewin, 2003).

Environmental concerns with the use of genetically modified crops
In genetically modified crops, there is a raised concern for the transfer of genes from cultivated species to their wild relatives. Yet, many plants are not local to the places in which they are grown. Locally, they may also have no wild relatives to which genes can flow. If the gene flow takes place, it is doubtful that hybrid plants would bloom in the wild, as they would have the features that are beneficial in agricultural environments only.

A debate also has arisen regarding whether genetically modified plants could hurt not only insects but also other species such as monarch butterfly.

Effects of Genetically modified crops on animals
Animal feeds often include genetically modified foods and enzymes derived from genetically modified micro-organisms. Feed mixtures are mainly used for pigs, poultry, and dairy cows, which contain a variety of elements, including corn and other cereals and oilseeds such as canola and soybeans (GreenFacts, 2004).

Personal statement
Genetically modified crops ensure sufficient food supply for the increasing population. These crops help the humans and environment in many ways. These are pest resistance, herbicide tolerance, disease resistance, cold tolerance, and drought tolerance (Whitman, 2000).

But, these genetically modified crops have many risks that fall into three categories human health risks, environmental hazards, and economic concerns. Environmental risks include harm to other organisms, decreased efficiency of pesticides, and transfer of genes to non-target species. Human health risks include Allergies, and other unknown effects.

There are many benefits and risks with genetically modified crops. However, we must proceed with care to prevent causing unintentional damage to health of humans and the environment (Whitman, 2000).