Thursday, June 14, 2007

Genetically Modified Foods

What Are Genetically Modified Foods?
In our modern society where the world’s population is ever-growing and problems like hunger are becoming a great deal, advanced food science has been utilised to meet the world’s increasing demand of food sources and better food supplies worldwide. A genetically-engineered food is the answer.


How Are Foods Genetically Modified?
The popular method for genetic engineering of crop plants is natural gene transfer via an Agrobacterium tumefaciens vector, a bacterium normally found in soils. The transfer of the DNA (T-DNA) vector is made by inserting the desired gene fragment in between specific 25bp repeat domains in the bacterium.


Often mentioned to as transgenic crops, it makes use of recombinant DNA techniques to alter the genetic makeup of different organisms by combining different selected individual genes from a few organisms or by inserting valuable genes into plant genomes. The resulting organism is then said to be “genetically modified”. Genetically modified (GM) foods include medicines and vaccines, foods and food ingredients as well as feeds and fibers.


Genes which are often selected to undergo genetic modification into a new modified food product are often valuable, selected ones with important traits, such as those which are present with natural insect resistance or desired nutrients. Therfore, genetic engineering allows genetic material to be transferred between any organism, including between plants and animals. For example, the gene from a fish that lives in very cold seas has been inserted into a strawberry, allowing the fruit to be frost-tolerant and maintain its natural goodness.


The expression of the gene introduced can also be controlled by adding additional sequences that might allow the gene to be constitutively expressed, expressed only in certain cell types, or expressed as a result of different environmental changes. This method of gene transfer, however, will only work for the natural host range of the bacterium and therefore other methods are used for additional crop plants. Such methods are uptake of naked DNA by electroporation or particle gun bombardment. The use of genetic markers allows for the preferential growth of cultures that contain the new genetic material.


Types of Genetically Modified Crops
Foods have been modified to make them resistant to insects and viruses and more able to be herbicide- and insecticide-resistant. Crops that have been modified for these purposes, with approval from the relevant authorities, in a number of countries, include:

• Maize
• Soybean
• Oilseed rape (Canola)
• Cotton
• Corn
• Squash
• Potato


Others included rice with increased iron and vitamins which may alleviate chronic malnutrition in third-world countries as well as plant crops which can survive drastic weathers.


Producing food which are tolerant to herbicides is one of the largest uses of plant genetic engineering. For example, there are crops which are genetically modified to be tolerant to glyphosphate. Glyphosphate is a synthetic herbicide and is the active ingredient in a kind of herbicide called Roundup®. Glyphosphate works by inhibiting the enzyme 5-enolpyruvyl-3-phosphoshikimic acid synthase (EPSPS), resulting in a disruption of the plants’ biosynthesis and ultimately death of the plant crop. A two-fold method has been used to produce crops that are glyphosphate-resistant. One part of the method uses recombinant DNA techniques to introduce plants that encode a glyphosphate-resistant EPSPS enzyme and the other introduces an enzyme that inactivates glyphosphate, glyphosphate oxidoreductase (GOX). (OCDE, 1999) Since crops are highly sensitive to glyphosphate, it was normally used as a pre-crop emergence herbicide. These new resistant cultivars will allow application both before and after crops emerge, with little to no crop damage. Plants that have been field-tested include beets, corn, cotton, lettuce, poplar, potato, rapeseed, soybean, tobacco, tomato, and wheat.


Modified genes may be present in many whole foods, referring to products such as soybeans, maize and tomatoes. Genetically modified food ingredients are also present in some foods. For example, soy flour in bread may have come from imported GM soybeans.


Modified genes may also have been used in an early stage of the food chain, but may or may not be present in the end product. Gene products - for example, phytochemicals (plant chemicals that contain compounds which may prevent disease) - may, however, remain in the food chain. This could be an advantage or a disadvantage.


Advantages of genetic engineering versus traditional plant breeding
There are four main advantages of genetically engineering plants over traditional methods. First, the source of the DNA is not limited to related wild plants. It may come from other plant species, animal, microorganisms, or even lab synthesized genes. Next, transfer of new genes is more direct and does not require many generations of breeding to recover the new cultivar. Also, while traditional methods of gene transfer may result in the transfer of closely linked or unwanted genes, genetic methods allow for a more discrete transfer of a single valuable gene. Lastly, new gene constructs can be made, using molecular biology techniques, which could not be found in wild plants used for traditional breeding.


Further Controversies Surrounding GM Foods
Technologies for genetically modifying (GM) foods offer dramatic promise for meeting some areas of greatest challenge for the 21st century. Like all new technologies, they also poses some risks, both known and unknown. Controversies surrounding GM foods and crops commonly focus on human and environmental safety, labeling and consumer choice, intellectual property rights, ethics, food security, poverty reduction, and environmental conservation.


References:
http://www.ornl.gov/sci/techresources/Human_Genome/elsi/gmfood.shtml

http://www.nyu.edu/classes/jaeger/genetically_modified_foods.htm

http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/
Genetically_modified_foods?OpenDocument

1 Comments:

Blogger manju said...

The contribution of WHO and FAO as international bodies to this can also be added. Also the role of Codex Allimentarious Commission.

October 17, 2008 at 10:27 PM

 

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