Genetic engineering

corn kernels

Genetic engineering is the process of inserting DNA from one organism into another, either the same species or a different one, by artificial means. In plants, this can be done using a “gene gun” (which blasts the foreign piece of DNA into the genome of the plant) or using a bacterial system. Agrobacterium tumefaciens is a naturally occurring bacteria found in soil that was discovered to have the ability to transfer some of its own DNA to plants that it has infected. Scientists learned to take advantage of this bacterial system and it is now used to transfer small pieces of targeted DNA (for example, a particular gene of interest) to plants to create plants that contain the new gene(s).

While conventional plant breeding using cross-pollination can often accomplish the same result (a plant that carries a new or different gene), genetic engineering can sometimes be a much quicker – and more exact - method, and may work where conventional breeding cannot (e.g. inserting genes of different species that couldn’t cross-pollinate in nature).

An example of where genetic engineering has been very useful is in adding disease resistance genes to crops. In maize, the corn borer is an insect that causes great damage. A bacterium, Bacillus thuringiensis, was discovered to contain a toxin that is deadly to insects such as the corn borer. This toxin has been widely used in insecticides since the 1920s, and is considered to be safer and more environmentally friendly than many other insecticides, as it is so specific to a particular type of insect. Since the 1980s, genetic engineering has been used to insert the gene that produces this toxin into crops, including maize and cotton. “Bt Maize,” as it is called, is widely grown in the U.S. and South Africa, and has been approved for use in Europe. This application of genetic engineering has not only been useful to farmers in preventing corn borers from devastating crops, but has also greatly reduced the use of pesticides on corn and cotton throughout the world.

The number of pesticide sprayings in the Mississippi Delta region dropped by half just within the first year that Bt cotton became widely used. In the US, the volume of pesticide used on maize was decreased by 12% due to the use of Bt maize.

Genetic engineering is controversial. Some people feel it is unnatural to use biotechnology to create plants that most likely would not occur in nature. They have questions about the safety of these new plants, will they might become invasive weeds, or might people may have allergies to them. These are real questions, but are as relevant to conventional plant breeding (which also results in new crop varieties) as to genetically modified organisms, or GMOs. For example, maize itself would never have occurred in nature! Studies are ongoing worldwide to address the issues related to GMO’s.  So far genetically engineered crops have been shown to have the same levels of safety and allergic reactions as non-GMOs, or less, and may have benefits, especially in areas of hunger and malnutrition, that can’t be disregarded. These techniques could also be used to add in genes that improve nutritional qualities, drought tolerance, etc.

Myths of genetic engineering

  • “Biotechnology” = transgenics or GMOs. Creating genetically modified organisms is one type of biotechnology but there are many others. The PCR (polymerase chain reaction) technique, genetic fingerprinting, and the use of molecular markers and Marker Assisted Selection are examples of biotechnology that are not GMO related.
  • DNA is inherently unique to each organism and introduced, therefore “foreign” DNA, can be identified as being from another organism. All biological organisms are made of strings of the same four nucleotides (adenine, guanine, cytosine and thymine). We cannot identify “foreign” (that is, from another organism) simply by looking at the DNA sequence of an organism. This can only be done by having a priori knowledge of the complete DNA sequences of each, and/or knowledge of the method of insertion of the foreign DNA.
  • GMOs will cause food allergies. Many foods cause allergies in some people. New varieties have been created through conventional plant breeding that some people are allergic to. There is no evidence that food created via the transgenic approach will create more food allergies; on the contrary, some food allergens may be eliminated with this approach.
  • Transgenic plants are less “natural” and may be dangerous (“monster weeds”). New plant varieties can be created using conventional plant breeding to be more vigorous and weedy; there is nothing inherent in the transgenic approach to create this. Any new plant varieties, no matter the method of creation, can be tested and managed to avoid this problem.
  • People in poor countries are having GMOs forced on them without their knowledge and consent. Most countries have policies in place to monitor GMOs. In many countries, GMOs are widely accepted; in particular, GMO plants that have new genes which allow them to grow in harsh conditions, such as under drought or particular disease stress.

When we look at the whole picture—using a systems approach—employing modern molecular (including GMO) and breeding techniques to engineer crops can help reduce human disease and hunger, increase crop yield therefore reducing the amount of acreage used for farming, reduce pesticide and fertilizer use which reduces a major form of pollution in the environment, etc.  Regulation and oversight on these processes are in place and should be continually monitored.  These techniques can not only help people around the world avoid disease and hunger, but also help to reduce our use of resources and greatly reduce our impact on the environment.<\p>

The bottom line: genetically modified organisms should be developed thoughtfully and monitored carefully, like all food crops, but can have extremely beneficial uses. <\p>

Examples of genetically-modified organisms:

  • Insulin-producing bacteria (the 1st commercial GMO, 1978)
  • Yeast producing HepB vaccine
  • Roundup ready soybean (resistant to an herbicide)
  • Bt corn, cotton, and potato (confers insect resistance)
  • Golden rice (increased Vitamin A)
  • Faster growing salmon
  • Non-allergenic cats
  • Glo-fish (the first transgenic animals to be sold as pets)

Brookes G and Parfoot P (2006) GM crops: the first ten years – global socio-economic and environmental impacts. PG Economics Ltd. UK