Biology
Genetically Modified Foods
Lam Ka Wai
2-9-2001
What is ‘old biotechnology’ in reference to food plants ?
All plant breeding(人工培育) involves genetic manipulation(操控) of plants and all have been genetically modified through traditional plant breeding techniques--such as cross fertilization(配種) of selected plants--to produce desired traits(特質). This is "old biotechnology."
What is "new biotechnology" in reference to food plants ?
The new biotechnology,or genetic engineering-is actually an extension of traditional plant breeding. It involves direct modification of DNA, a living thing‘s genetic material. This new technique is more precise, making it possible to direct and predict changes without introducing extraneous(額外的), undesirable traits. The new technique also will allow scientists to introduce genes from essentially any organism into a plant.
What is GMOs?
Living things which have been genetically modified are known as genetically modified organisms (GMOs).
How to modified modify organism genetically?
1. 2.
At first,scientists use a special enzyme to cut the genes wanted in the DNA of some organism,the enzyme is so called’biological scissors’.Then the genes is inserted into the DNA of some bacteria or virus because they can duplicate themselves rapidly. Then,the modified bacteria or virus will be put into the organisms which are being genetically modified.There are two methods to put the bacteria or virus into the organism: Infection - for plants; Injection - for animals.
Why do we need these plants and the foods they produce?
Plant breeders have a limited pool of genes--and, therefore, traits,available for use in improving plants. By looking at bacteria and animals, scientists can find other traits that may expand the number of potentially useful traits. These may include size, solids content, or resistance to certain viruses or fungi.
What benefits will these genetically engineered plants have ?crop yields Increase
Increase the tolerance of crops to adverse growing conditions, e.g. drought Improve the nutrient composition of crops, e.g. increase the protein content of rice Provide resistance to crop pests and reduce the use of pesticides Improve sensory attributes of food, e.g. flavour, texture Improve processing characteristics so as to reduce wastage and costs
Eliminate allergy(過敏)-causing properties in some foods
Details
Generally more work has been done to date on plants, with the main focus on improving crop yield and quality. For example:
Examples
1.
2.
using a flounder(魚:鰈)gene to make a tomato freeze and thaw better. That protein also is being used as a model for developing a food additive to use in ice cream so ice crystals don't form. To make food safer by reduce the natural toxins and to eliminate allergy-causing properties in some foods e.g. to identify the allergenic proteins in foods like milk.
3. Insect resistant - crop plants genetically engineered to resist certain insect pests. So reduce the use of pesticides. e.g. They produce toxin proteins using genes from a soil bacterium, Bacillus thuringiensis (Bt). In their natural form, Bt toxins are lethal to the larvae of certain pests but not to other living things.
4. Virus resistant - plants genetically engineered to resist certain viruses. They often use genes which code(指定遺傳密碼) for proteins actually found in viral coats. These are intended to 'prime' the plant to fight the real virus when it is encountered, but are specific to a particular group of viruses.
5. Crop plants genetically modified to resist other pests, like fungi or roundworm. 6. Plants genetically modified for delayed ripening(成熟), longer shelf-life, or to tolerate(抵抗) adverse growing conditions e.g. drought(乾旱).
7. Improve the nutrient composition of crops, e.g. increase the protein content of rice 8.Transgenic animals – they are genetically engineered for leaner(瘦) meat, enhanced growth rates, or production of 'enhanced' milk (milk that contains useful substances). 9. Micro-organisms used in food processing (such as bacteria in yoghurt).
10. Transgenic mammals such as goats(山羊) and cows are being used to produce 'enriched' milk. For example, one variety of cow produced a protein found in human breast milk in her milk, and this may be sold as a formula for premature babies. 11. In micro-organisms, specific proteins from bacteria are being explored for use as food preservatives(防腐劑).
12. Improve processing characteristics so as to reduce wastage and costs.
13.Increase crop yields and cheaper price. To help the people in the third world.
Salmon Genetically Engineered with Growth Hormone Genes Something fishy is going on in the American Northwest: Salmon are being genetically engineered to grow twice as fast, so they can be sold sooner and are therefore more profitable. These gene-altered fish pose threats to wild fish, our rivers and oceans, and our dinner plates. These threats are irreversible, once genetically engineered fish escape into open waters, they can never be recalled.
The Case of Genetically Modified Tomato Paste
Genetically modified tomato paste was marketed to cater for consumer choice and information needs, and to provide a clear consumer benefit (it was cheaper than normal tomato paste).
Risks
Are there environmental risks involved in producing genetically altered foods? unintended modification of similar species in the neighbouring fields due to cross pollination disturbing the balance of ecosystems development of super pests whether it is acceptable to move genes between plants or animals which do not normally interbreed Ethical(道德) or religious implications (牽連).
Details
1. potential transfer of traits to other plants and potential may have adverse effects on other organisms . For example, if a plant has many wild relatives, it could pass a gene to one of those, resulting in an outcross plant species with some undesirable traits. The wild plants could develop into a fast-growing weed species, for instance. Whether outcrossing is a problem depends on the trait that's introduced, as well.
2. allergies.
Example:
The Case of the Brazil Nut Soybean In the early 1990s, one of the world's largest seed companies, Pioneer Hi-Bred, developed a more nutritious type of soybean by adding a gene taken from Brazil nuts. The project was dropped when it was discovered that the novel soybean would trigger a major attack in people with Brazil nut allergies.
3. Ethical(道德) or religious implications (牽 連). some people may worry about eating a food containing a gene from something they would not eat for religious, health or other reasons
Situation in HK
新聞稿 香港，2001年8月21日－綠色和平今天協助警方 將五個涉嫌含有基因改造成份的巨型雀巢公司產 品帶返灣仔警務處，以利有關當局作進一步調查。 五個真人比例的雀巢產品模型包括百福鮮豆漿、 百福豆腐花、甘脆朱古力、嬰兒純米粉(蘋果味)、 以及鳳仙雪條。過去兩年，綠色和平先後五次在 食品測試中發現雀巢產品含基因改造成份。
雀巢牛奶香港有限公司決定，屬下產品將 逐步停用來自基因改造生物的成分，並表 示研究基改造生物對農業生的影響。…… 雀巢公司在奧地利，德國，英國，比利時 和法國等六個地區，亦早已宣布放棄基因 改造生物作為生材料。 (二oo一年五月廿九日 星期二 蘋果日報 )
Genetically modified foods in HK
雀巢即溶奶粉 雀 巢甘 脆 朱 古 力 雀 巢 ( 百 福 鮮 豆 漿、百 福 豆 腐 )
好 立 克 三 合 一、阿 華 田 三 合 一
公 仔 麻 油 麵 公 仔 麵 、公 仔 海 鮮 碗 麵 Dreyer's Grand Ice Cream (Toasted Almond) 、明 治 花 生 巧 克 力 脆 皮 雪 糕
Foods made with soy, including tofu(豆腐), are likely to contain genetically modified organisms (GMOs). Greenpeace 1999
Future Plan
As the range of GM foods available on the market increases, the issue of better enabling consumers to make informed choices by labelling is receiving priority concern. The Food and Environmental Hygiene Department is studying the feasibility of setting up a GM food labelling system.
IS GM FOOD SAFE TO EAT?
. The answer is that nobody knows because long term tests have not been carried out. despite the absence of such tests a wide range of problems have already been encountered and many more have been predicted.
Opinions
1. 2.
Genetically modified foods can help people,it needs time for people to know more about it and accept it. Genetically modified foods should be reviewed carefully. require labeling : Potential allergens. nutritional content of the food is changed.
Ethical(道德) or religious implications (牽連)
How about the ethical or religious implications of injecting animal genes into plants? And how will this affect vegetarians?
There are thousands of genes in a plant. When a scientist adds new genes from an animal, it gives that plant several new proteins. But these proteins would not seem to give animal characteristics to the vegetable. One of the things people probably don't realize is that there are genes in humans and animals that are in plants. There is a gene that occurs in rice that also occurs in the human brain. Vegetarians would not avoid rice because of that.
Data
A number of foods from genetically modified sources are already on the market. More are expected over the next few years:
In the USA, 48 food products derived from genetically modified crops have been approved by government. American consumers can eat genetically modified tomatoes, potatoes, strawberries, and food products made from genetically modified soy, corn and more.
In Japan, 20 genetically modified crop varieties have been approved. In Europe, eight.
A heated debate is being waged about genetically modified foods internationally. Amongst the fray are scientists, environmental groups, industry bodies, consumer groups and farmers.
Reference
Us food and drug administration http://www.fda.gov/bbs/topics/consumer/Con001 91.html Australian Broadcasting Corporation http://www.abc.net.au/science/slab/consconf/ Genetically modified foods http://www.info.gov.hk/fehd/safefood/gmf/left.ht ml
Genetic food alert http://www.geneticfoodalert.org.uk/ http://www.info.gov.hk/fehd/safefood/gmf/left.ht ml Greenpeace(綠色和平基因工程網頁) /http://www.greenpeacechina.org.hk/ge/links.htm
Useful Websites:
GM Online http://library.thinkquest.org/C004033F/link _text.htm