In layman's terms, it is a process in which genes in one organism are transferred to another organism or to different varieties of the same organism. Generally speaking, transgene is achieved through sexual reproduction. For example, plant pollen "runs" from one plant to another through different media, or "runs" to the pistil in the flower of another variety of the same plant and hybridizes with it. This hybridization process produces gene transfer. Similarly, taking cats as an example, different breeds and types of cats have different offspring from their parents after mating, which is due to gene transfer. Therefore, transgene occurs every day in nature, but in nature, gene transfer has no goal, and both good and bad genes can be transferred to different biological individuals together. At the same time, the transgene through natural hybridization is strictly controlled within the same species or between closely related plant species.
Second, the safety of genetically modified food.
1, Lancet Magazine199910 16 reported that a. puz tai of Rowett Institute, Scotland (1998) first used the transgenic potato with snowdrop lectin (GNA). 10 days later, the feeding group was found. He thinks it may be the result of introducing genes to activate or prevent other genes in plants.
2. In 2002, a human residue test of genetically modified food DNA was conducted in Britain. Seven volunteers who had undergone surgery to remove large intestine tissue ate hamburgers made of genetically modified soybeans, and the residual DNA of transferred genes was detected in their small intestine bacteria.
3. The experiment of transgenic potato was carried out in Britain from 65438 to 0998. After continuous feeding of transgenic potatoes, rats' organs grew abnormally, lost weight and their immune system was destroyed. This caused a sensation all over the world at that time, but by 1999, there were also different opinions, saying that some methods and statistics were problematic.
However, some people think that genetically modified food is safe, and the safety of genetically modified food is controversial all over the world. Some people think that this problem may not be confirmed or falsified for a long time. Different people have different views on transgenic technology from different angles, which is the root of many controversies. Almost any food contains genes. Regardless of the origin of the gene, the DNA (deoxyribonucleic acid) that constitutes the gene will be decomposed into small molecules by enzymes after entering the human body, so it is impossible to bring foreign genetic information into the human genome. From this perspective, there is no difference between genetically modified food and traditional food. Like traditional food, genetically modified food is safe.
Third, the drawbacks and shortcomings of transgenic technology
1, the main deficiency of transgenic technology itself.
(1), loose technology: Gene technology transfers a heterologous gene from one organism to another. Although its DNA can be accurately cut, it cannot accurately implant new genes into another organism, thus affecting the basic functions of other genes in this organism. Scientists can't predict the new unknown protein after plant genotyping, and they can't predict the immature effect on the receptor completely and accurately.
(2) Side effects: Gene technology is just like a surgeon performing heart surgery. Scientists can't fully know in advance that DNA surgery on living things may lead to mutation and harm to the environment and people. Although the experiment is very mature, we can't grasp all the information that may affect human beings in the face of the strong pressure of nature.
(3) Large-scale crop yield reduction: Gene technology gains profits by constantly selling seeds, which means that when farmers plant transgenic seeds, all the plants planted have the same genes. When fungi, viruses and pests attack these special plants, serious yield reduction will occur.
(4) Seriously affect the whole food supply: insects, birds and wild animals will carry transgenic seeds to nearby fields. When transgenic plants produce pollen, they will cross-pollinate transgenic crops and wild animals, and all crops, organic matter or inorganic matter are easily polluted by cross-pollination.
2. Health hazards
(1), the safety test has not been conducted for a long time: genetically modified food has changed the natural properties of the food we eat, and the biological substances it uses are not the part provided by human food safety. No one knows whether this food is safe without long-term safety test.
(2) Toxin production: Genetically modified food will produce unpredictable biological mutation, which will produce higher levels and new toxins in food. L After spraying transgenic Bt corn pollen on the leaves of a plant milkweed, the edible leaves of Papilio Papilio grew slowly, and the mortality rate of larvae was 44% in 4 days. However, none of the control group (leaves fed with Bt corn pollen) died. Insecticidal toxins produced by genetically modified crops can penetrate from the roots to the surrounding areas, but it is not clear what effect they will have.
(3) Allergy or allergic reaction: Genetic technology will produce unpredictable and unknown allergens in food. It is reported that subjects who are allergic to Brazil nuts are also allergic to soybeans genetically modified with this nut. Scientists transplanted the characteristics of Brazilian walnuts to soybeans, but as a result, some people who are allergic to walnuts may be allergic when eating soybeans. Phytocoagulants are toxic to some pests, and genetically modified foods must not contain such toxic substances.
(3) Reducing the nutritional value of food or degrading important ingredients in food: The purpose of genetics is to remove or inactivate substances that people think are unnecessary. These substances may be unknown, but they are basic. For example, it has a natural ability to inhibit cancer (Pariza, M.W., 1990). American research data show that in soybeans with herbicide-resistant genes, anti-cancer components such as isoflavones are reduced. The false freshness of genetically modified foods confuses consumers. Red tomatoes with fragrance and luster can be preserved for several weeks, but their nutritional value is low. When consumers buy fruits or vegetables, they can't accurately judge the true quality of the products only by appearance and texture. Transgenic microorganisms disturb the natural circulation of nutrients in the environment.
(5) Antibiotic-resistant bacteria: Gene technology uses antibiotic-resistant genes (such as kanamycin, ampicillin, neomycin, streptomycin, etc.). ) to identify transgenic crops, that is, crops have antibiotic resistance genes. These genes affect us through bacteria. British research shows that mutant genes in genetically modified crops may enter organisms. If the mutant gene crosses the population and is transferred to bacteria, the result may lead to new diseases. Although this probability is very small, if there is an incurable and widely spread disease that poses a serious threat to life, the consequences will be unimaginable. According to the experimental results published by Dutch scientists in New Scientist magazine, an artificial stomach was designed to simulate the process of human digestion of genetically modified food. It was found that DNA remained in the intestine, and some genetically modified bacteria could transfer their antibiotic resistance genes to the bacteria in the artificial stomach. If similar results happen to humans and animals, it is possible to cultivate the most powerful superbacteria that antibiotics cannot kill. The British New Food and Technology Advisory Committee has banned the trend of feeding a genetically modified corn with ampicillin resistance gene to cattle, because the DNA contained in it remains intact and may accelerate the resistance to antibiotics.
(6) The problem cannot be traced back: if it is not marked, our public health authorities will not be able to find the source of the problem, and the potential harm is doubtful.
(7) Side effects can be fatal: Mayeno, A.N. et al. (1994) reported a new disease of unknown cause, mainly manifested as eosinophilic myalgia. Clinical manifestations include paralysis, neurological problems, pain and swelling, itchy skin, heart problems, memory loss, headache, light sensitivity and emaciation (Brenneman, D.E. et al.,1993; Love, L.A., etc., 1993). It was later discovered that tryptophan was produced by genetically engineered bacteria born in a Japanese company. Three months later, the eater fell ill, resulting in 37 deaths, 1, 500 people were partially paralyzed, and more than 5,000 people were occasionally weak. According to the determination, the content of 0. 1% can kill people.
3. Direct harm
The Lancet magazine199910 June16 reported that Puztai, A. (1998) of Rowett Institute in Scotland first fed mice with potatoes with the gene of snowdrop lectin (GNA). After 10 days, it was found that the mucosa of colon, jejunum and some small intestine in the feeding group was thickened. He thinks it may be the result of introducing genes to activate or prevent other genes in plants. In addition, it was observed that the kidney, thymus and spleen of experimental rats grew abnormally or atrophied or grew improperly, and many important organs were also destroyed, the brain shrank and the immune system weakened. Although the Royal British Medical Association has conducted an investigation on this special organization of scientists, it believes that the experiment has many defects in design, implementation, analysis and so on, and it should not be premature to draw conclusions. Although there are differences between the two groups, these differences can not explain the problem because of the limitation of experimental technology and the incorrect use of statistical methods. But it still can't dispel people's doubts about genetically modified food. After the recombinant cow production hormone (rbGH) was put into commercial use in the United States, users quickly found that this kind of drug led to an increase in the incidence of mastitis in dairy cows and a low reproductive rate. Due to the effect of drugs, the metabolism of dairy cows is accelerated, resulting in increased energy consumption and death. The nutritional value of milk has also decreased. Scientists have conducted targeted research on genetically modified corn and cotton that have been approved for commercial cultivation in Spain and the United States, and believe that genetically modified crops may cause meningitis and other new diseases. It is also confirmed that genetically modified food may induce cancer and pass it on to the next generation, which may take 30 years or more.
Whether transgenic therapeutic drugs and human tissues and organs have an impact on human health. We can't test for confirmation yet.
4. Environmental impact
(1), the use of herbicides has increased: scientists estimate that transgenic crops are resistant to herbicides, and the actual use is three times higher than normal. Farmers know that their crops are resistant to herbicides and will use a lot of herbicides.
(2) Increased use of pesticides: Genetically modified crops often use their own unique pesticides, which are classified as pesticides by the US Environmental Protection Agency, which means that more pesticides enter our food and fields than before. It has been reported that implanting excellent specific genes (such as pesticide resistance) into crops may improve the surrounding wild plants and make them show the characteristics of pesticide resistance.
(3) Ecological destruction: GEO affects the local ecological environment through the food chain, and new microorganisms compete effectively with related organisms, causing intangible damage to the environment. As an artificial genetically modified crop, it may become an exotic variety that does not exist in nature. After several years, it may cause damage to soil, wild relatives, ordinary crops, adjacent plants and the environment.
(4) Genetic pollution is difficult to eliminate: genetically modified organisms, bacteria and viruses cannot be preserved or recovered after entering the environment. Unlike chemical or nuclear pollution, the side effects are irreversible.
(5) Transgenic crops can turn wild relatives into weeds and become "super weeds" through gene flow. It has been proved that 93% of the germinated offspring seeds are proved to be interspecific weeds when there are related weeds nearby after the release of transgenic rapeseed.
(6) Harmful to non-target organisms and threatening biodiversity: Hilbeck( 1998) fed the European corn borer (ECB) with transgenic Bt corn as the feed for lacewings, while GN fed ordinary corn as the control. The experimental results showed that the mortality rate of transgenic Bt corn group was above 60%, while that of control group was below 40%. It is considered that the factors related to Bt are related, and the maturity time of surviving Chrysopa in Bt corn group is 3 days later than that in control group on average. The experimental results of Birch, A. et al. (1996/7) showed that feeding aphids with transgenic potatoes reduced the number of eggs laid by females 1/3. When male aphids fed with transgenic potatoes mated with aphids in the control group, the number of unfertilized eggs was four times higher, and the mortality rate of fertilized eggs before hatching was nearly three times higher than that in the control group. The survival time of female mosquitoes fed with transgenic potato aphids is better than that of the control group
Fourthly, the prospect of genetically modified food.
In fact, genetically modified food is not without its merits. It's just that it's difficult to guarantee its safety at the current level of biotechnology. In fact, it is an irresistible trend to improve crop quality through transgenic technology, because there are many problems that cannot be solved by conventional breeding, especially the cultivation of drought-tolerant and barren crop varieties. For example, in the desert areas of Africa, if the current farming methods are used, its grain output can not meet the basic living security at all. People now hope to produce some crops that are more drought-tolerant and barren-tolerant through transgenic technology, so as to solve the pressure brought by the reduction of cultivated land. In addition, transgenic technology can improve the nutritional composition of crops. Now, a very famous example is golden rice, which is produced by transferring the key genes of β -carotene synthesis pathway into rice. This kind of rice contains synthetic raw materials of vitamin A, which is helpful to treat diseases such as blindness caused by vitamin A deficiency, which is very important for developing countries. Therefore, transgenic technology still has broad development prospects.