What Is Genetic Engineering?

Genetic engineering is a laboratory technique used by scientists to change the DNA of living organisms.

DNA is the blueprint for the individuality of an organism. The organism relies upon the information stored in its DNA for the management of every biochemical process. The life, growth and unique features of the organism depend on its DNA. The segments of DNA which have been associated with specific features or functions of an organism are called genes.

Molecular biologists have discovered many enzymes which change the structure of DNA in living organisms. Some of these enzymes can cut and join strands of DNA. Using such enzymes, scientists learned to cut specific genes from DNA and to build customized DNA using these genes. They also learned about vectors, strands of DNA such as viruses, which can infect a cell and insert themselves into its DNA.

With this knowledge, scientists started to build vectors which incorporated genes of their choosing and used the new vectors to insert these genes into the DNA of living organisms. Genetic engineers believe they can improve the foods we eat by doing this. For example, tomatoes are sensitive to frost. This shortens their growing season. Fish, on the other hand, survive in very cold water. Scientists identified a particular gene which enables a flounder to resist cold and used the technology of genetic engineering to insert this 'anti-freeze' gene into a tomato. This makes it possible to extend the growing season of the tomato.

What are the Dangers?

Fundamental Weaknesses of the Concept Imprecise Technology—A genetic engineer moves genes from one organism to another. A gene can be cut precisely from the DNA of an organism, but the insertion into the DNA of the target organism is basically random. As a consequence, there is a risk that it may disrupt the functioning of other genes essential to the life of that organism.

Side Effects—Genetic engineering is like performing heart surgery with a shovel. Scientists do not yet understand living systems completely enough to perform DNA surgery without creating mutations which could be harmful to the environment and our health. They are experimenting with very delicate, yet powerful forces of nature, without full knowledge of the repercussions.

Widespread Crop Failure—Genetic engineers intend to profit by patenting genetically engineered seeds. This means that, when a farmer plants genetically engineered seeds, all the seeds have identical genetic structure. As a result, if a fungus, a virus, or a pest develops which can attack this particular crop, there could be widespread crop failure.

Threatens Our Entire Food Supply—Insects, birds, and wind can carry genetically altered seeds into neighboring fields and beyond. Pollen from transgenic plants can cross-pollinate with genetically natural crops and wild relatives. All crops, organic and non-organic, are vulnerable to contamination from cross-pollinatation. (Emberlin et al 1999) Health Hazards No Long-Term Safety Testing—Genetic engineering uses material from organisms that have never been part of the human food supply to change the fundamental nature of the food we eat. Without long-term testing no one knows if these foods are safe.

Toxins—Genetic engineering can cause unexpected mutations in an organism, which can create new and higher levels of toxins in foods.

Allergic Reactions—Genetic engineering can also produce unforeseen and unknown allergens in foods.

Decreased Nutritional Value—Transgenic foods may mislead consumers with counterfeit freshness. A luscious-looking, bright red genetically engineered tomato could be several weeks old and of little nutritional worth.

Antibiotic Resistant Bacteria—Genetic engineers use antibiotic-resistance genes to mark genetically engineered cells. This means that genetically engineered crops contain genes which confer resistance to antibiotics. These genes may be picked up by bacteria which may infect us.

Problems Cannot Be Traced—Without labels, our public health agencies are powerless to trace problems of any kind back to their source. The potential for tragedy is staggering.

Side Effects can Kill—37 people died, 1500 were partially paralyzed, and 5000 more were temporarily disabled by a syndrome that was finally linked to tryptophan made by genetically-engineered bacteria. (Mayeno 1994) Environmental Hazards Increased use of Herbicides—Scientists estimate that plants genetically engineered to be herbicide-resistant will greatly increase the amount of herbicide use. (Benbrook 1999) Farmers, knowing that their crops can tolerate the herbicides, will use them more liberally.

More Pesticides—GE crops often manufacture their own pesticides and may be classified as pesticides by the EPA. This strategy will put more pesticides into our food and fields than ever before.

Ecology may be damaged—The influence of a genetically engineered organism on the food chain may damage the local ecology. The new organism may compete successfully with wild relatives, causing unforeseen changes in the environment.

Gene Pollution Cannot Be Cleaned Up—Once genetically engineered organisms, bacteria and viruses are released into the environment it is impossible to contain or recall them. Unlike chemical or nuclear contamination, negative effects are irreversible. DNA is actually not well understood. 97% of human DNA is called junk because scientists do not know its function. The workings of a single cell are so complex, no one knows the whole of it. Yet the biotech companies have already planted millions of acres with genetically engineered crops, and they intend to engineer every crop in the world.

The concerns above arise from an appreciation of the fundamental role DNA plays in life, the gaps in our understanding of it, and the vast scale of application of the little we do know. Even the scientists in the Food and Drug administration have expressed concerns.

A first introduction to genetic engineering About genes Genes are at the very heart of life. Together they constitute the blueprint of an organism. In computer terms they are the master program of life. They decide all the properties and all the capabilities of an organism.

In biological terms this master program is called the hereditary substance, the chromosomes. It is constituted by chains of so called DNA molecules that carry the "code words" or instructions of the master program.

There is an identical set of this master program in every cell. For example a corn plant has about a billion cells, each with a set of this master program. In different parts of the plants different parts of the program are active, giving rise to different structures like the leaves, the seeds and the root. The cell is like a huge computer network, much larger than any man-made one. Science has a very incomplete understanding how this billion of master programs is able to cooperate in a very harmoniously and effectively coordinated way.

Genetic engineering: Genetic engineering means manipulation of this master program. Genes, mostly from other, often totally unrelated species are inserted in the genetic "master program". Genes from e.g. fish, scorpions, bacteria and viruses have been inserted into food plants in genetic engineering projects.

The method of genetic engineering is so crude that it is impossible to decide beforehand where the inserted genes will stick in the master program. The effect of a gene is greatly dependent on the properties of its neighboring genes. This is one of several reasons why the outcome of artifical gene insertion (genetic engineering) are unpredictable. It is an established scientific fact that such manipulation may in the worst case lead to the creation of harmful substances as well as other unexpected disturbances.

The knowledge about genes is very incomplete In addition, the knowledge about the master program is very incomplete. Actually only 2-3 percent of it are so called genes. Their function is fairly well known. The function and purpose of the remaining 97-98 percent is very little known.

From genetics it is well known that even changing just a little code word in the master program can mean the difference between health and a deadly hereditary disease. So the genes are very powerful.

It is probably not a coincidence that an unproportionately large part of our members are computer experts. They know that the addition of just one "code syllable" (binary code) may be disastrous to a computer program. Haphazard insertion of genes, as done in genetic engineering, does not add just one syllable, but many thousand of code syllables. In addition, it is obvious to a computer scientist that it is absolutely vital to completely master the program in order to be able to make a useful change in a reliable way. For some obscure reason, this is regrettably not obvious to biotechnology researchers. They are manipulating genes although they are very far from mastering the genetic "program".

Much too little is know to justify commercial use We find it irresponsible to use genetic engineering for commercial purposes at this stage of very incomplete knowledge about the effects. Especially so as harmful substances may be generated. Also, very little is known what artificially manipulated genes released into nature may do to the environment.

Conclusion It is an undeniable fact that science knows much too little about the effects of genetic engineering to be able to predict and master the consequences. Therefore genetic engineering has to be confined to contained laboratories until science knows what it is doing. By using it for foods at this stage means an inevitable risk for unexpected and potentially harmful effects on human health as well as for the environment.

Although a there has been a tremendous revolution in the biological sciences in the past twenty years, there is still a great deal that remains to be discovered. The completion of the sequencing of the human genome, as well as the genomes of most agriculturally and scientifically important plants and animals, have increased the possibilities of genetic research immeasurably. Expedient and inexpensive access to comprehensive genetic data has become a reality, with billions of sequenced nucleotides already online and annotated. Now that the rapid sequencing of arbitrarily large genomes has become a simple, if not trivial affair, a much greater challenge will be elucidating function of the extraordinarily complex web of interacting proteins, dubbed the proteome, that constitutes and powers all living things. Genetic engineering has become the gold standard in protein research, and major research process has been made using a wide variety of techniques, including

loss of function, such as in a knockout experiment, in which an organism is engineered to lack one or more genes. This allows the experimenter to analyze the defects caused by this mutation, and can be considerably useful in unearthing the function of a gene. It is used especially frequently in developmental biology. A knockout experiment involves the creation and manipulation of a DNA construct in vitro, which, in a simple knockout, consists of a copy of the desired gene which has been slightly altered such as to cripple its function. The construct is then taken up by embryonic stem cells, where the engineered copy of the gene replaces the organism's own gene. These stem cells are injected into blastocysts, which are implanted into surrogate mothers. Another method, useful in organisms such as drosophila, is to induce mutations in a large population and then screen the progeny for the desired mutation. A similar process can be used in both plants and prokaryotes. gain of function experiments, the logical counterpart of knockouts. These are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. The process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or attracting more frequent transcription. 'tracking' experiments, which seek to gain information about the localization and interaction of the desired protein. One way to do this is to replace the wild-type gene with a 'fusion' gene, which is a juxtaposition of the wild-type gene with a reporting element such as green fluorescent protein that will allow easy visualization of the products of the genetic modification. While this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. More sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences which will serve as binding motifs to monoclonal antibodies.

Proponents of genetic engineering argue that the technology is safe, and that it is necessary in order to maintain food production that will continue to match population growth. However, others argue that food distribution, not production, is the biggest problem, citing that the population growth is actually a result of uneven distribution of food (and wealth).

Others oppose genetic engineering on the grounds that genetic modifications may have unforeseen consequences, both in the initially modified organisms, and their environments. For example, certain strains of maize have been developed that are toxic to plant eating insects (see bt corn). However, when those strains cross-polinated with other varieties of wild and domestic maize, the relevant genes were passed on. This introduced a new gene into the gene pool of the maize population outside of the crop field. The ecological and environmental effects of transgenic plants are constantly being investigated.

Anti-genetic-engineering activists say that with current recombinant technology there is no way to ensure that genetically modified organisms will remain under control, and the use of this technology outside of secure laboratory environments carries unacceptable risks for the future.

Some fear that certain types of genetically engineered crops will further reduce biodiversity in the cropland; herbicide-tolerant crops will for example be treated with the relevant herbicide to the extent that there are no wild plants ('weeds') able to survive, and plants toxic to insects will mean insect-free crops. This could result in declines in other wildlife (e.g. birds) which depend on weed seeds and/or insects for food resources. The recent (2003) farm scale studies in the UK found this to be the case with GM sugar beet and GM rapeseed, but not with GM maize (though in the last instance, the non-GM comparison maize crop had also been treated with environmentally damaging pesticides subsequently (2004) withdrawn from use in the EU).

Proponents of current genetic techniques as applied to food plants cite the benefits that the technology can have, for example, in the harsh agricultural conditions of third world countries. They say that with modifications, existing crops would be able to thrive under the relatively hostile conditions providing much needed food to their people. Proponents also like to cite golden rice, a genetically engineered rice variety (still under development) that contains elevated vitamin A levels. There is hope that this rice may alleviate vitamin A deficiency that contributes to the death of millions annually.

Proponents say that genetically engineered crops are not significantly different from those modified by nature or humans in the past, and by extension are as safe or even safer than such methods. There is gene transfer between unicellular eukaryotes and prokaryotes. There have been no known genetic catastrophes as a result of this.

Economic and political effects Many opponents of current genetic engineering believe the increasing use of GM in major crops has caused a power shift in agriculture towards Biotechnology companies gaining excessive control over the production chain of crops and food, and over the farmers that use their products, as well.

Many proponents of current genetic engineering techniques believe it has brought higher yields and profitability to many farmers, including those in third world countries.

In April 2004 Hugo Chávez announced a total ban on genetically modified seeds in Venezuela.

Cloning is the process of creating an identical copy of an original. A clone in the biological sense, therefore, is a multi-cellular organism that is genetically identical to another living organism. Sometimes this can refer to "natural" clones made either when an organism reproduces asexually or when two genetically identical individuals are produced by accident (as with identical twins), but in common parlance the clone is an identical copy by some conscious design. Also see clone (genetics).

The term clone is derived from κλων, the Greek word for "twig". In horticulture, the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o". Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively.

In biology, cloning is used in two contexts: cloning a gene, or cloning an organism. Cloning a gene means to extract a gene from one organism (for example by PCR) and insert it into a second organism (usually via a vector), where it can be used and studied. Cloning a gene sometimes can refer to success in identifying a gene associated with some phenotype. For example, when biologists say that the gene for disease X has been cloned, they mean that the gene's location and DNA sequence has been identified, although the ability to specifically copy the physical DNA is a side-effect of its identification.

Cloning an organism means to create a new organism with the same genetic information as an existing one. In a modern context, this can involve somatic cell nuclear transfer in which the nucleus is removed from an egg cell and replaced with a nucleus extracted from a cell of the organism to be cloned (currently, both the egg cell and its transplanted nucleus must be from the same species). As the nucleus contains (almost) all of the genetic information of a lifeform, the "host" egg cell will develop into an organism genetically identical to the nucleus "donor". Mitochondrial DNA, which is not transferred by this process, is generally ignored as its effects on organisms are thought to be relatively minor.

The term clone is used in horticulture to mean all descendants of a single plant, produced by vegetative reproduction. Many horticultural varieties of plants are clones, having been derived from a single individual, multiplied by some process other than sexual reproduction. As an example, some European varieties of grapes represent clones that have been propagated for over two millennia. This is a genuine example of cloning in the broader biological sense, as it creates genetically identical organisms by biological means, but this particular kind of cloning has not come under ethical scrutiny and is generally treated as an entirely different kind of operation.

Therapeutic cloning is the procedure for creating stem cells genetically compatible with the patient.

However, the success rate has been very low: Dolly was born after 276 failed attempts; 70 calves have been created from 9,000 attempts and one third of them died young; Prometea took 328 attempts. With certain species such as dogs no successful clones have been created at all.

A surprising development to do with aging resulted from finds that Dolly was apparently born old; she developed arthritis at age six. Aging of this type is thought to be due to telomeres, regions at the tips of chromosomes which prevent genetic threads fraying every time a cell divides. Over time telomeres get worn down until cell-division is no longer possible - this is thought to be a cause of aging. However, when researchers cloned cows they appeared to be younger than they should be. Analysis of the cow's telomeres showed they had not only been 'reset' to birth-length, but they were actually longer - suggesting these clones would live longer life spans than normal cows (but many have died young after excessive growth). Researchers think that this could eventually be developed to reverse aging in humans.

Human cloning is a subject of great controversy regarding its ethical and practical consequences. Many people believe that attempts to perform human reproductive cloning would be unethical, but some scientists have publicly announced their intention to do so. A number of groups have made claims that they are working on or have already produced human clones. None of these claims has been independently confirmed. Meanwhile therapeutic cloning appears to be a promising technology for combating many deadly deseases. For more on these issues, see the article human cloning.

Cloning extinct species has been a dream of scientists for decades. This pursuit was publicized in Jurassic Park, but has come closer to being a reality in recent years (in fact, the dinosaurs in Jurassic Park were not really cloned -- their genomes were reconstructed from bits and pieces of many dinosaur genomes). One of the most anticipated targets for cloning was once the Woolly mammoth, but attempts to extract DNA from frozen mammoths have been unsuccessful.

In 2000, a cow named Bessie gave birth to a cloned Asian guar, an endangered species; this provided hope that similar techniques (using surrogate mothers of another species) might be used to clone extinct species; in anticipation of this possibility, the last bucardo, a Spanish mountain goat, was frozen immediately after it died (from illness after birth). Researchers are also considering cloning endangered species such as the giant panda, ocelot, and cheetah.

In 2002, geneticists at the Australian Museum announced that they had replicated DNA of the Thylacine (Tasmanian Tiger), extinct about 65 years previous, using polymerase chain reaction (PCR).

One of the continuing obstacles in the attempt to clone extinct species is the need for nearly perfect DNA. Furthermore, if animals were cloned from one individual, the significant problem of lack of genetic diversity would still remain in the attempt to establish a breeding population

While the promise cloning extinct species is an old justification for developing cloning, there are a lot of other applications. One is cloning cattle, horses and other domestic animals. This appears to be a much faster and more efficient way to propagate good genes (as chosen by humans) than traditional breeding.

Another application that has recently became feasible is cloning pets. Little Nicky was the first pet cloned (by the Genetic Savings and Clone company) after the death of the original. The procedure is still very expensive and the demand is in its infancy, though. But there is potential demand in many unexpected areas.

An expression vector is a relatively small DNA molecule that can be used to carry a specific gene into a target cell. Once the expression vector is inside the cell, the protein that is coded for by the gene is produced by the normal transcription and translation processes of the host cell. Expression vectors are used for molecular biology techniques such as site-directed mutagenesis. In general, DNA vectors that are used in many molecular biology gene cloning experiments need not result in the expression of a protein. Expression vectors are often specifically designed to contain non-protein-coding sequences that act as enhancer and promoter regions and allow efficient transcription of the gene that is carried on the expression vector. Expression vectors are basic tools for biotechnology and the production of proteins such as insulin that are important for medical treatments of specific diseases like diabetes.

Gene expression is the multi-step process by which a gene's information is converted into the structures and functions of a cell, following the central dogma of molecular biology.

Gene therapy is the insertion of genes into an individual's cells and tissues to treat a disease, and hereditary diseases in particular. Gene therapy typically aims to supplement a defective mutant allele with a functional one. Although the technology is still in its infancy, it has been used with some success. Antisense therapy is not strictly a form of gene therapy, but is often lumped together with them.

In the 1980s, advances in molecular biology had already enabled human genes to be sequenced and cloned. Scientists looking for a method of easily producing proteins, such as the protein deficient in diabetics — insulin, investigated introducing human genes to bacterial DNA. The modified bacteria then produce the corresponding protein, which can be harvested and injected in people who cannot produce it naturally.

Scientists took the logical step of trying to introduce genes straight into human cells, focusing on diseases caused by single-gene defects, such as cystic fibrosis, hemophilia, muscular dystrophy and sickle cell anemia. However, this has been much harder than modifying simple bacteria, primarily because of the problems involved in carrying large sections of DNA and delivering it to the right site on the genome.

In theory it is possible to transform either somatic cells (most cells of the body) or cells of the germline (such as stem cells, sperm and eggs). All gene therapy so far in people has been directed at somatic cells, whereas germline engineering in humans remains only a highly controversial prospect. For the introduced gene to be transmitted normally to offspring, it needs not only to inserted into the cell, but also to be incorporated into the chromosomes by recombination.

Somatic gene therapy can be broadly split in to two categories: ex vivo (where cells are modified outside the body and then transplanted back in again) and in vivo (where genes are changed in cells still in the body.) Recombination-based approaches in vivo are especially uncommon, because for most DNA constructs recombination is a very low probability event.

The ex vivo approach was the first to be put in to practice. In 1990 trials were run designed to treat children with an inherited immune defficiency, as well as children or adults with high serum cholesterol. Cells were removed from the patients body and incubated with vectors that inserted copies of the genes. Most gene-therapy vectors are viruses, although there are techniques for delivering DNA directly as well. After modification, the cells are transplanted back in to the patient where they will hopefully replicate and produce functional descendants for the life of the transplanted individual.

This technique is best used for diseases where the desired cells can be extracted easily, such as the blood or liver.

For in vivo techniques the challenge of inserting the genes is even greater. The vector carriers have a difficult task to complete: they must deliver the genes to enough cells for results to be achieved and they have to remain undetected by the body's immune system.

Much hope has been placed in viruses to deliver the DNA. After all, this is what viruses do naturally — insert their genes into cells so that their hosts can reproduce them. Through millions of years of evolution viruses have developed very sophisticated ways of doing this. There are two classes of viruses which look promising — retroviruses and adenoviruses.

Genetic engineering, genetic modification (GM), and gene splicing (once in widespread use but now deprecated) are terms for the process of manipulating genes in an organism, usually outside of the organism's normal reproductive process. It often involves the isolation, manipulation and reintroduction of DNA into model organisms, usually to express a protein. The aim is introduce new genetic characteristics to an organism to increase its usefulness such as, increasing the yield of a crop species, introducing a novel characteristic, or producing a new protein or enzyme. c, g. Examples are the production of human insulin through the use of modified bacteria and the production of new types of mice like the OncoMouse, (cancer mouse) for research, through genetic redesign.

Retroviruses are small RNA based viruses. Because they reproduce by integrating their RNA into the host's DNA, they carry the prospect of incorporating new genes into chromosomes, so that cells that divide will pass the genes to their progeny. Scientists have removed certain crucial genes from the viral genome, so that they cannot damage the host. RPR Gencell (a French pharmaceutical company) conducted experiments injecting retroviruses into lung cancer patients. After the injections of vectors containing p53 — a gene that suppresses tumours — directly in to the cancerous tissue, the tumours stopped growing and were broken down by the body.

Adenoviruses are larger, DNA-based viruses, which can carry more genes.

A problem affecting all virus-based vectors is recognition by the immune system. When familiar viruses are detected in the bloodstream the body sends antibodies to bind to and consume them. In retroviral and other recombination-based approaches, a second problem arises in the unpredictablity of where the new DNA inserts into the chromsomes of transfected cells. If the gene is inserted in a bad place — for example within the sequence of an important gene, or within non-coding (intron) regions that the cell will never use to produce proteins (transcribe) — then the new gene would not be properly expressed and the cell could be made worse or even cancerous.

Scientists are researching an interesting way of bypassing the DNA problems by actually introducing an extra chromosome into the body. Existing alongside existing DNA, this 47th chromosome would contain the genes needed. Introduced into the body as a large vector, it is not expected to be targeted by the immune system because of its construction.

Viruses attack their hosts to insert their genetic material into the genetic material of the host. This genetic material contains instructions to produce these viruses. The host cell will carry out these intructions and produce the viruses. This is how viruses spread, in general.

In addition to the instructions producing the components of the virus itself, viruses can carry additional genes containing instructions for creating other kinds of proteins. In theory, if we insert a gene that is missing from a patient in a virus, and infect that patient with the virus, the virus will spread the missing gene in all the cells of the patient. The missing gene is now replaced and the disease is cured. This technique is called gene therapy.

Three types of viruses are currently used as vectors in gene therapy: retroviruses and adenoviruses and adeno-associated viruses. They differ in their mechanisms of action and results.

The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes into the cell. This RNA molecule from the retrovirus must produce a DNA copy from its RNA molecule before it can be considered part of the genetic material of the host cell. The process of producing a DNA copy from an RNA molecule is termed reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. d, k, d. After this DNA copy is produced and is free in the nucleus of the host cell, it must be incorporated into the genome of the host cell. That is, it must be inserted into the large DNA molecules in the cell, or the chromosomes of the cell. This process is done by another enzyme carried in the virus called integrase.

Now that the genetic material of the virus is incorporated and has become part of the genetic material of the host cell, we can say that the host cell is now modified to contain a new gene. When this host cell divides later, its descendants will all contain the new genes.

One of the problems of gene therapy using retroviruses is that the integrase enzyme can insert the genetic material of the virus in any arbitrary position in the genome of the host. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted. If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur.

Gene therapy trials to treat severe combined immunodeficiency (SCID) were halted or restricted when leukemia was reported in several of the patients.

Adenoviruses are viruses that carry their genetic material in the form of DNA. When these viruses infect a host cell, they introduce their DNA molecule into the host. The genetic material of the adenoviruses is not incorporated into the host cells genetic material. The DNA molecule is left free in the nucleus of the host cell, and the instructions in this extra DNA molecule are transcribed just like any other gene. The only difference is that these extra genes are not replicated when the cell is about to undergo cell division. So the descendants of that cell will not have the extra gene. This means that treatment with the adenovirus will require regular doses to add the missing gene every time new cells are produced without the gene.

Adeno-associated viruses, from the parvovirus family, are small viruses with a genome of single stranded DNA. There are a few disadvantages to using AAV, mainly the small amount of DNA it can carry and the difficulty in producing it. This type of virus is being used, however, because it is non-pathogenic (most people carry this harmless virus). In contrast to adenoviruses, most people treated with AAV will not build an immune response to remove the virus and the cells that have been succesfully treated with it. Several trials with AAV are on-going or in preparation, mainly trying to treat muscle and eye diseases, the two tissues where the virus seems particularly useful

For the safety of gene therapy, the Weismann barrier is fundamental in the current thinking. Soma-to-germline feedback should therefore be impossible. However there are indications that the Weissman barrier can be breached.

The Weismann barrier is the principle that hereditary information moves only from genes to body cells but never in reverse. In more precise terminology hereditary information moves only from germline cells to somatic cells (or soma to germline feedback is impossible). This is often confused with the central dogma of molecular biology which in its modern form states that information travels from DNA<->RNA->protein.

Since a protein is specified by a DNA segment or gene, future copies of that protein can be modified by changing the gene's underlying DNA. One way to do this is to isolate the DNA, cut it, and splice in a different DNA segment. Daniel Nathans and Hamilton Smith received the 1978 Nobel Prize in physiology or medicine for their isolation of restriction endonucleases, which are able to cut DNA at specific sites. Together with ligase, which can join together fragments of DNA, restriction enzymes formed the initial basis of recombinant DNA technology. i, l, j, g, a. Genetic modification or genetic manipulation are claimed to be neutral and possibly more technically correct terms for what is claimed, controversially, to be genetic engineering. Opponents question whether the concept of 'modification', with its implications of progress, are applicable here.

The theory is very important as it has implications for human gene therapy. If the Weismann barrier is permeable then genetic treatments of somatic cells may actually result in an inheritable change to the genome, possibly resulting in the genetic engineering of the human species rather than just individuals. It also has implications in our understanding of evolution as it would imply that species aren't nearly as separable genetically as we once thought. Furthermore it opens the door to the existence of certain Lamarckian concepts that previously had no supporting mechanism.

The work of 19th century biologist August Weismann was an early step in the founding of the science of genetics, and like any part of any science is subject to review in light of new data. Although the principle was seriously questioned at times in the 20th century, the attacks of Paul Kammerer and Trofim Lysenko did nothing to weaken the principle among scientists, except where science was ruled by arbitrary political power under Stalin.

In the late 20th century there have been criticisms of an impermeable Weismann barrier. These criticisms are all centered around the activities of an enzyme called reverse transcriptase.

Evidence has begun to mount for horizontal gene transfer. Different species appear to be swapping genes through the activities of retroviruses. Retro-viruses are able to transfer genes between species because they reproduce by integrating their code into the genome of the host and they often move nearby code in the infected cell as well. Seeing as these viruses use RNA as their genetic information they need to use reverse transcriptase to convert their code into DNA first. If the cell they infect is a germline cell then that integrated DNA can become part of the gene pool of that species.

Other evidence against Weismann's barrier is found in the immune system. A controversial theory of Edward J. Steele's suggests that endogenous retroviruses carry new versions of V genes from soma cells in the immune system to the germ line cells. This theory is expounded in his book Lamarck's signature. Edward J Steele observes that the immune system needs to be able to evolve fast to evolutionary pressure (as the infective agents evolve very fast). He also observes that there are plenty of endegenous retro-viruses in our genome and it seems likely that they have some purpose.

It should be noted that even if both of these possible exceptions turn out to be real the Weismann barrier just loses its absolute status. Without further examples the penetration of the Weismann barrier is still very much an exception.

A genetically modified food is a food product containing some quantity of any genetically modified organism (GMO) as an ingredient. They are mainly to increase the mass of food to feed more people.

Some nations have very strong disagreement over genetically modified organisms. For example, the European Union and Japan are willing to maintain labelling and traceability standards for GM food products, while the United States claims it violates free trade agreements.

The first commercially grown genetically modified food crop was a tomato created by Calgene called the FlavrSavr. Calgene submitted it to the U.S. Food and Drug Administration for testing in 1992; following the FDA's determination that the FlavrSavr was, in fact, a tomato, did not constitute a health hazard, and did not need to be labeled to indicate it was genetically modified, Calgene released it into the market in 1994, where it met with little public comment.

Subsequent genetically modified food crops included virus-resistant squash, a potato variant that included an organic pesticide called Bt (NB: the EPA classified the Bt potato as a pesticide, but required no labeling), strains of canola, soybean, corn and cotton engineered by Monsanto to be immune to their popular herbicide Roundup, and Bt corn.

There was a brief interlude where Monsanto flirted with introducing a technology called terminator into food crops, which produced plants that grew sterile seeds. Monsanto claimed this was necessary to protect their intellectual property rights, since they were licensing the technology to farmers, and would also have provided a measure of protection against volunteer corn carrying unwanted traits, a major concern that arose during the Starlink debacle.

Public outcry about the undue influence that the terminator gene would give to Monsanto, particularly in less developed nations where seed saving is more common, led to its withdrawal.

Awareness grew throughout the nineties and eventually produced a strong backlash against GM foods (discussed below), which were panned as "untested", "unlabeled" and "unsafe"; following this backlash, the International Rice Research Institute, with funding from the Rockefeller Foundation developed a strain of rice enriched with vitamin A through genetic modification, dubbed golden rice. Subsequently the biotech industry touted this as a boon to poor people suffering from Vitamin A deficiency, which can cause blindness. This was condemned by GM food opponents as a ploy and a public relations move. (See golden rice for more.)

Many prominent environmental organizations, like Friends of the Earth and Greenpeace, currently consider the issue of the presence of GMOs in conventional food products to be a major issue - indeed Greenpeace has made it a centerpiece of their activism. In 2002, opponents placed a measure on the Oregon ballot that would have made that state the first to require labelling of GMO food.

Between 1996 and 2002, the total surface area of land cultivated with GMOs has increased by a factor of thirty. Land producing GMO crops grew from 17,000 km² (4.2 million acres) in 1996 to 520,000 km² (128 million acres) in 2001. The value for 2002 was 145 million acres (587,000 km²) and for 2003 was 167 million acres (676,000 km²). Soybean crop represented 63% of total surface in 2001, maize 19%, cotton 13% and canola 5%.

Four countries represent 99% of total GM surface in 2001: United States (68%), Argentina (22%), Canada (6%) and China (3%). It is estimated that 70% of products on U.S. grocery shelves include GM products. In particular, Bt corn is widely grown, as are soybeans genetically designed to tolerate Monsanto's Roundup herbicide.

The US Agriculture Department estimated that 38 percent of the 79 million acres (320,000 km²) of corn planted in 2003 will be genetically engineered varieties as well as 80% of the 73.2 million acres (296,000 km²) soybeans.

Complicating the issue, the majority of GM crops grown today are fed to animals, thereby indirectly effecting human food production.

Although "biotechnology" and "genetic modification" commonly are used interchangeably, GM is a special set of technologies that alter the genetic makeup of such living organisms as animals, plants, or bacteria. Biotechnology, a more general term, refers to using living organisms or their components, such as enzymes, to make products that include wine, cheese, beer, and yogurt. Combining genes from different organisms is known as recombinant DNA technology, and the resulting organism is said to be "genetically modified," "genetically engineered," or "transgenic." GM products (current or in the pipeline) include medicines and vaccines, foods and food ingredients, feeds, and fibers.

Locating genes for important traits—such as those conferring insect resistance or desired nutrients—is one of the most limiting steps in the process. However, genome sequencing and discovery programs for hundreds of different organisms are generating detailed maps along with data-analyzing technologies to understand and use them.

Transgenic crops are grown commercially or in field trials in over 40 countries and on 6 continents. In 2000, about 109.2 million acres (442,000 km²) were planted with transgenic crops, the principal ones being herbicide- and insecticide-resistant soybeans, corn, cotton, and canola. Other crops grown commercially or field-tested are a sweet potato resistant to a virus that could destroy most of the African harvest, rice with increased iron and vitamins that may alleviate chronic malnutrition in Asian countries, and a variety of plants able to survive weather extremes.

On the horizon are bananas that produce human vaccines against infectious diseases such as hepatitis B; fish that mature more quickly; fruit and nut trees that yield years earlier, and plants that produce new plastics with unique properties.

In 2000, countries that grew 99% of the global transgenic crops were the United States (68%), Argentina (23%), Canada (7%), and China (1%). Although growth is expected to plateau in industrialized countries, it is increasing in developing countries. The next decade will see exponential progress in GM product development as researchers gain increasing and unprecedented access to genomic resources that are applicable to organisms beyond the scope of individual projects.

Many opponents of the use of the term 'genetic engineering' argue the operations of genes in combination with cell biochemistry are rather poorly understood and sometimes lead to unexpected side effects. Reluctance to recognize this field as "engineering" has become popular in the anti-globalization movement and safe trade movement, and is also widely held by most Green parties, and the major parties of France and Germany, which have resisted any agricultural policy favoring genetically modified food. j, c, g, k, c. These groups tend to resist the label 'engineer' as applied to such genetic modification most strongly.

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 pose 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, eth