Genetic engineering


from Wikipedia, the free encyclopedia
Mice under UV light. In the middle an unchanged mouse, on the left and right animals that have been genetically modified in such a way that they form green fluorescent protein in some parts of the body .

When genetic engineering is referred methods and procedures of biotechnology based on the knowledge of molecular biology and genetics build and targeted intervention in the genetic material (genome) and thus in the biochemical control processes of living organisms or viral allow genomes. The product initially created is recombinant DNA , which in turn can be used to produce genetically modified organisms (GMOs). The term genetic engineering encompasses the modification and recomposition of DNA sequences in vitro (e.g. in a test tube) or in vivo (in living organisms). This also includes the targeted introduction of DNA into living organisms.

Genetic engineering is used to produce newly combined DNA within a species as well as across species boundaries. This is possible because all living beings use the same genetic code , which is only slightly deviated from in a few exceptional cases (see codon usage ). The aims of genetic engineering applications are, for example, the modification of cultivated plants, the manufacture of drugs or gene therapy .

Although there are great similarities in the methods used, a distinction is often made according to the area of ​​application:

meaning

Crops

Transgenic crops have gained in importance worldwide since they were first approved in 1996 and were cultivated in 28 countries on 179 million hectares (around 12% of the global agricultural area of ​​1.5 billion hectares) in 2015. In particular, these are plants that, due to genetic modifications, are tolerant of pesticides or toxic to certain harmful insects. For farmers, especially in developing countries, their use has resulted in yield, income and health benefits or reduced workloads and reduced environmental pollution, despite higher spending on seeds. Approved varieties are scientifically certified as being harmless to the environment and health. Environmental associations, suppliers of organically produced products and some political parties reject green genetic engineering.

Animals

Transgenic animals are mainly used as experimental animals in research. Transgenic animals for human consumption and for the containment of infectious diseases are not yet approved.

Medicine and pharmacy

A number of products that are of interest to humans ( e.g. insulin , vitamins ) are manufactured with the help of genetically modified bacteria. Genetic engineering has also gained importance in medicine, and the number of genetically engineered drugs on the market is steadily increasing. At the beginning of 2015, 175 medicinal products with 133 different genetically engineered active ingredients were approved in Germany. They are used for a wide range of diseases, such as diabetes , anemia , heart attacks, growth disorders in children, various types of cancer and hemophilia . Over 350 genetic engineering substances are in clinical trials with patients worldwide.

Insulin is the best known hormone that was obtained with the help of genetic engineering. The insulin used earlier came from cattle and pigs and was not one hundred percent identical to that of humans. It has now been replaced by genetic engineering and, among other things, has solved the problems of diabetics with an intolerance to animal insulin.

Genetically engineered drugs are also established today in cancer therapy. According to some cancer experts, the use of interferon and hematopoietic growth factors could improve cancer therapies for certain types of tumors, shorten or even avoid hospital stays and improve quality of life.

Approaches to the genetic modification of cells in the human body for healing purposes are described in the article Gene Therapy .

history

About 8000 years ago was in what is now Mexico by breeding the genomes of teosinte -Cereals by combining naturally occurring mutations altered so that the predecessor of today's corn emerged coals. This not only increased the yield, but also created fungus resistance.

Artificial mutations for breeding purposes were created within conventional agriculture by exposing germs to strong ionizing radiation or other gene-changing influences ( mutagens ) in order to cause mutations in the genetic material more frequently than under natural conditions. Seeds were sown, and those plants that possessed the desired properties were further grown. It was not systematically checked whether other, undesirable, properties also developed. This technique was used with almost all useful plants and also with some animal species, but the success of mutation breeding in plants was only between 0.5 and 1% of mutants that could be used for breeding purposes; in animals this method cannot be used at all.

In these forerunners of genetic engineering, however, the modified organism did not contain any recombinant DNA .

Autoradiography of a sequencing gel. The DNA shown was radioactively labeled with 32 P ( phosphorus ).

The real history of genetic engineering began when Ray Wu and Ellen Taylor succeeded in 1971 in using restriction enzymes discovered in 1970 to separate a sequence of 12 base pairs from the end of the genome of a lambda virus . Two years later, the first genetically modified recombinant bacterium was created by introducing a plasmid with combined viral and bacterial DNA into the intestinal bacterium Escherichia coli . In light of this progress, the Asilomar Conference was held in Pacific Grove , California , in February 1975 . At the conference, 140 molecular biologists from 16 countries discussed safety requirements under which research should continue. The results formed the basis of government regulations in the United States and later in many other states. In 1977 the genetic engineering of a human protein in a bacterium succeeded for the first time . In the same year Walter Gilbert , Allan Maxam and Frederick Sanger independently developed methods for efficient DNA sequencing , for which they were awarded the Nobel Prize in Chemistry in 1980. At the end of the 1970s, the Belgians Marc Van Montagu and Jeff Schell discovered the possibility of introducing genes into plants using Agrobacterium tumefaciens and thus laid the foundation for green genetic engineering.

In 1980 Ananda Chakrabarty applied for the first patent on a GMO in the USA , the approval process of which was carried out before the Supreme Court . In 1981 he decided that the fact that micro-organisms are alive had no legal significance for the purpose of patent law and thus paved the way for the patenting of living beings. In 1982, insulin, the first genetically engineered drug, came onto the market in the United States. In 1982, the bacteriophage lambda, the first virus in its complete DNA sequence, was published. In 1983, Kary Mullis developed the polymerase chain reaction , with which DNA sequences can be duplicated, and received the 1993 Nobel Prize in Chemistry for this. In 1985, genetically manipulated plants became patentable in the USA and the first release of genetically manipulated bacteria (ice minus bacteria) took place. In 1988, the first patent for a genetically modified mammal, the so-called crab mouse , was granted.

From autumn 1990 the human genome project began to sequence the entire human genome . On September 14, 1990, the world's first gene therapy was carried out on a four-year-old girl. In 1994, genetically modified Flavr Savr tomatoes were launched in the United Kingdom and the United States .

In 1996, transgenic soybeans were first grown in the US. The import of these soybeans to Germany led to the first public controversy there about the use of genetic engineering in agriculture. Greenpeace carried out several illegal protests in autumn 1996, such as obstructing the deletion and labeling of freighters.

In 2001, Celera and the International Genetics & Health Collaboratory claimed to have completely deciphered the human genome in parallel with the Human Genome Project. However, the sequencing was not complete. A year later, the first genetically engineered primate was born in its germline .

Techniques by area of ​​application

The generation of genetically modified organisms usually consists of two methods. The recombinant DNA is generated by cloning . Depending on the vector used, a method for introducing the DNA is then required, e.g. B. by transfection or transformation . The genome editing used in addition sequence-specific endonucleases . Here is an overview of the most important techniques:

Polymerase chain reaction (PCR)
The polymerase chain reaction (short: PCR) is a universal process for the replication of a DNA segment, the beginning and end of which are known. Using these short pieces of sequence and the enzyme DNA polymerase , the corresponding part of the “template” is duplicated in a single step, with several steps following each other quickly. Each copy created can be used as a template in the next step. After z. B. 20 steps or "cycles" has increased the number of originally existing sequence copies by 10 6 times. The number of original molecules can therefore be very small; For a genetic fingerprint, a successful PCR has already been carried out on the genetic material that a suspect left on a doorbell.
DNA sequencing
DNA sequencing is based on PCR , with the help of which the sequence of the individual nucleotides of a DNA sequence can be determined. A piece of DNA is amplified (duplicated) using PCR. In contrast to normal PCR, however, four reactions are set up in parallel here. In addition to the usual nucleotides (dNTPs) that allow the DNA strand to be lengthened, each batch also contains a proportion of so-called ddNTPs that lead to strand breakage. The individual PCR products are separated on a gel according to type (A, C, G or T) and position in the sequence. The evaluation of the gel then gives the nucleotide sequence of the DNA. By automating this process and organizing individual DNA fragments in a long strand using bioinformatics, it has already been possible to sequence many complete genomes, including that of humans.
Cloning
Often a gene is supposed to be transferred from one organism to another. This horizontal gene transfer is z. B. essential for human insulin to be produced by bacteria; the insulin gene has to be transferred into the bacterium. In addition, the gene must get to the right place in the target organism so that it can be used correctly there. The extraction of the original DNA usually takes place via PCR. At the same time, certain sequences are incorporated at the ends of the DNA. These sequences can then be recognized by restriction enzymes. These enzymes act like molecular scissors; they cleave DNA at specific sequences, leaving characteristic "sticky" ends ( sticky ends ). These “stick” to matching sequences that were generated in the target organism with the same restriction enzymes. Certain enzymes ( ligases ) can reassemble the matching sticky ends to form a continuous DNA sequence - the gene has been precisely incorporated.
Gene knockout
The function of a gene is often best recognized when it is not working. By comparing the phenotypes of two organisms with a functioning or defective gene, at least the fundamental importance of this gene becomes apparent. For this reason, knockouts are often used, i.e. living beings in which a certain gene has been deliberately made unusable. There are also so-called knock-out strains, organisms that inherit a certain defect. Knock-out strains are critical to many studies; so z. B. Examine carcinogenesis well in mouse strains that have a knock-out in one or more tumor suppressor genes.
DNA chips
DNA chips are becoming increasingly important in research and diagnostics . Such a chip (which has nothing to do with computer chips apart from its shape) has dozens or hundreds of small chambers, each of which contains exactly one short piece of DNA. This corresponds to z. B. a characteristic piece of a disease-causing genetic defect in humans. If human DNA is now placed on the chip, this DNA hybridizes with the matching counterparts on the chip. Hybridized DNA can then be made visible in color. From the position of the color signals, conclusions can now be drawn about the hybridizations and thus about the state of the added DNA; In this example, genetic predispositions for certain diseases can be diagnosed. A variant of the DNA chips are the RNA chips, in which mRNA is used for hybridization. This allows conclusions to be drawn about protein expression patterns.

Applications

Green genetic engineering (agro-genetic engineering)

Elements of genetic engineering: bacterial culture in a dish, seeds and DNA fragments made visible by electrophoresis

Since the function of most genes in plants is unknown, in order to recognize them one has to modify the control of the gene. The effects of genes are usually tried to elucidate by comparing three plant populations (wild type, overexpressors and “knockout” population). There are various techniques for this, such as RNAi . All techniques have in common that they produce double-stranded RNA, which gives the plant the “command” to break down the “normal” ribonucleic acid of the gene to be examined.

Descriptive techniques are also standard equipment in genetic engineering plant research. This involves cloning genes, then determining the frequency of transcripts (instructions for building proteins) or, using so-called DNA chips , the reading frequency of most of a plant's genes.

The Agrobacterium -mediated gene transfer is also an important technique. With this genetic engineering method, individual genetic factors are transferred from cells of one organism to cells of another living being.

The somatic hybridization in turn makes it possible to combine desired characteristics of different parent plants. In comparison to the Agrobacterium-mediated gene transfer, no specific genes have to be identified and isolated. In addition, this overcomes the restriction of transformation (gene transfer) that only a few genes can be introduced into a given genetic material. The number of chromosomes in the cells can also be multiplied during cell fusion , i.e. the number of chromosome sets ( degree of ploidy ) can be increased. This can increase the productivity of plants ( heterosis effect ). Molecular markers or biochemical analyzes are used to characterize and select plants that have emerged from somatic hybridization.

Red genetic engineering

Gene therapy is a genetic engineering method used in red biotechnology . Here an attempt is made to cure diseases that are caused by defective genes by exchanging these genes.

  • In ex vivo gene therapy approaches, cells are removed from the patient, genetically modified and then returned to the patient.
  • In in vivo gene therapy approaches , the patient is treated directly with the correction DNA in a vector (e.g. retroviruses ), which is intended to establish the DNA in the genome of the target cells.

Biotechnological drugs are produced by transgenic organisms (microorganisms, farm animals or pharmaceutical plants ). Changes are made iteratively until an active ingredient is created that can cure the disease.

White genetic engineering

By controlled evolution, strains of microorganisms are generated and, based on their yields, the desired products, which have been determined by screening , are selected. This process is repeated in iterative cycles until the desired changes are achieved. To identify organisms that cannot be cultivated, one examines metagenomes , ie the entirety of the genomes of a habitat, biotope or community ( biocenosis ). In metagenomes, for example, biocatalysts can be found that catalyze previously unknown biochemical reactions and form new, interesting metabolic products.

To introduce plasmid DNA into the bacterium, u. a. the property of calcium chloride used to make cell membranes permeable.

Labelling

EU

Since April 18, 2004, there has been an obligation to label genetically modified products within the EU . It includes that all products that have a genetic modification must be labeled, even if the modification can no longer be detected in the end product. Meat, eggs and dairy products from animals that have been fed with genetically modified plants as well as product additives that have been produced with the help of genetically modified bacteria, as well as enzymes , additives and flavors , are excluded from the labeling requirement , as they are not considered food in the legal sense.

In this context, critics of genetically modified foods point out that currently (as of 2005) around 80 percent of genetically modified plants cultivated are used in the animal feed industry . They are therefore calling for mandatory labeling for these animal products as well. Even if the genetic material of genetically modified feed is dissolved in the stomach of animals, it can be detectable in the end product, at least as fragments.

Furthermore, labeling does not have to be carried out if the contamination with genetically modified material is below 0.9% (as of 2008) percent by weight and is accidental or technically unavoidable. Each individual ingredient of a food or feed must be considered separately. In 2007 a new EU organic regulation (No. 834/2007) was passed, which will come into force in 2009. It creates the possibility that additives for food or feed that are A) generally approved in organic farming and B) are demonstrably not available in GMO-free quality may also be used if they have been produced by genetically modified microorganisms . The interpretation of the new rule is still pending. No substance is currently permitted under the new rule.

Genetic engineering labeling of products and ingredients
Products that consist of or contain GMOs "This product contains genetically modified organisms"; "This product contains [name of the organism / organisms], genetically modified"
Food without a list of ingredients "Genetically modified"; "Made from genetically modified [name of the organism]"
Ingredients in an ingredient list "Genetically modified"; "Made from genetically modified [ingredient name]"
Categories of ingredients in an ingredient list "Contains genetically modified [name of the organism]"; "Contains [name of the ingredient] produced from genetically modified [name of the organism]"
Regulation 1830/2003 on the traceability and labeling of genetically modified organisms

Germany

Liability, penal regulations and definitions in relation to genetic engineering are legally regulated by the German Genetic Engineering Act passed in 1990 . The second part of this law defines the safety levels and measures at workplaces for genetic engineering work. The classification is based on risk to human health and the environment in 4 security levels :

step description
S1 Genetic engineering work which, according to the state of the art, does not pose a risk to human health or the environment
S2 Genetic engineering work which, according to the state of the art, can be assumed to pose a low risk to human health or the environment
S3 Genetic engineering work which, according to the state of the art, can be assumed to pose a moderate risk to human health or the environment
S4 Genetic engineering work which, according to the state of the art, has a high risk or a justified suspicion of such a risk to human health or the environment

In case of doubt, after hearing a commission, the higher security level is selected for the assignment.

The genetic engineering safety ordinance regulates the precise handling of genetically modified organisms. A law to reorganize genetic engineering law was passed in June 2004 to implement the EU directive on the release of GMOs.

Austria

In Austria, the genetic engineering referendum was accepted in April 1997 . With a turnout of more than 21%, a legally anchored ban on the production, import and sale of genetically modified food , a ban on the release of genetically modified plants, animals and microorganisms as well as a ban on the patenting of living beings were called for. The resolution was adopted on April 16, 1998 after the third reading.

Switzerland

As part of a popular initiative on November 27, 2005, the majority of the Swiss people voted for a moratorium on the use of genetic engineering in agriculture, with a participation of over 42% . For an initial five years, the cultivation of plants or the keeping of animals that had been genetically modified was prohibited. The only exceptions are small cultivation areas for research (especially risk research) that are subject to the provisions of the Release Ordinance . Imports of genetically modified products are partly permitted - subject to strict conditions. After intensive political discussion, the moratorium was extended to 2013 by the Federal, State and National Council. Afterwards, the results of a national research program that ran until 2012 will be taken into account for a new decision-making process. With the same arguments, the moratorium was extended in December 2012 to the end of 2017. Despite the extension, the Federal Council wants to allow farmers to grow genetically modified plants in certain zones from 2018. However, these plans are met with fierce opposition in parliament. In Switzerland , the approval for biotechnologically produced rennet substitutes was already granted in 1988 by the Federal Office of Public Health . There is no obligation to declare that the cheeses produced in this way are considered GMO-free and are therefore not counted as genetically modified foods . The moratorium, which bans cultivation for agricultural purposes, has now been extended until the end of 2021. In March 2019, issued Federal Office for the Environment of the University of Zurich , the permit for a field trial with transgenic wheat .

Other countries

The regulation of genetic engineering is often less strict outside of the German-speaking countries and the EU in general. In the USA and Canada, labeling is e.g. B. voluntarily.

further reading

Web links

Commons : genetic engineering  - collection of images, videos and audio files
Wiktionary: Genetic engineering  - explanations of meanings, word origins, synonyms, translations

Individual evidence

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