Genetically Modified Crops and the Transferring of Genes
Heidi Groth
Genetic Engineering is the alteration of an organism's genetic, or hereditary, material to eliminate undesirable characteristics or to produce desirable new ones. Many of these new beneficial traits in plant varieties fight plant pests - insects, weeds and diseases - that can be devastating to crops. Others provide quality improvements, such as better tasting fruits and vegetables; processing advantages, such as tomatoes with higher solids content; and nutrition enhancements, such as oil seeds that produce oils with lower saturated fat content. The first-known genetic engineering technique, still used today, was the selective breeding of plants and animals, usually for increased food production. In selective breeding, only those plants or animals with desirable characteristics are chosen for further breeding. Corn has been selectively bred for increased kernel size and number and for nutritional content for about 7,000 years. More recently, selective breeding of wheat and rice to produce higher yields has helped supply the world's ever-increasing need for food.
In recent decades, genetic engineering has been revolutionized by a technique known as gene splicing. In gene splicing, one or more genes of an organism are introduced to second organism. This essentially alters the characteristics of the organism by changing its protein makeup.
The original process used to create transgenic crops is the biolistic method (gene gun) which consists of two 6” x 7” x 10” stainless steel chambers connected to a 2HP vacuum pump. The DNA to be delivered is attached to tiny gold or tungsten balls (1 micrometer in diameter). These balls are put onto a disk that is in the inside of the Gene Gun. A blast of helium at 1000 psi sends the disk shooting forward at approximately 1300 feet per second, roughly the same speed as a bullet leaving a rifle. A screen stops the disk and the tiny gold or tungsten balls are launched towards the target cells. The balls breech the cell membrane and release the DNA particles. This method used for the creation of the two most common transgenic crops - RoundUp ready soybean and Bt-corn.
A newer method being used is the Agrobacterium method. This uses bacteria to benignly infect the plant and transfer the desired genes during that process. In this method, the DNA region of the Agrobacterium that transfers DNA is removed from bacteria and replaced with the desired gene and a marker, which is then inserted into the organism.
Both methods use DNA markers to screen for cells that have successfully taken up the desired gene. Cells that have the new DNA and DNA marker will survive when exposed to a certain herbicide or antibiotic depending on which marker is used.
No whole plants are used in either method but plant cells. In order to obtain whole plants from these cells, they are grown under controlled environmental conditions in tissue culture. This is a process of a series of media, each containing nutrients and hormones, to introduce normal plant development. Once the plants are grown and produce seed, the evaluation of the progeny process begins. This process entails selection of the seeds with the desired traits and then retesting and growing to make sure that the entire process has been completed successfully with the desired results.