What is genetic engineering? brief introduction
Genetic engineering is an important branch of bioengineering, which constitutes bioengineering together with cell engineering, enzyme engineering, protein engineering and microbial engineering. Genetic engineering is a complex technology to manipulate genes at the molecular level. It is the operation of introducing foreign genes into recipient cells through in vitro recombination, so that the genes can be replicated, transcribed, translated and expressed in recipient cells. It is a brand-new technology. By artificially extracting the genetic material needed by the donor organism-DNA macromolecules, cutting them in vitro with appropriate tool enzymes, connecting them with DNA molecules as carriers, and then introducing them into recipient cells that are easier to grow and reproduce together with the carriers, so that foreign substances can "settle down" in them, and make normal replication and expression, thus obtaining new species.
Genetic engineering is a brand-new biotechnology science born on the basis of the comprehensive development of molecular biology and molecular genetics in 1970s. Generally speaking, genetic engineering refers to genetic engineering at the gene level. It is to artificially extract the genetic material of a donor organism-DNA macromolecule, cut it in vitro with an appropriate tool enzyme, connect it with the DNA molecule as a carrier, and then introduce it into the recipient cell which is easier to grow and reproduce together with the carrier, so that the foreign genetic material can "settle down" in it and be reproduced and expressed normally. This definition shows that genetic engineering has the following important characteristics: first, exogenous nucleic acid molecules can propagate in different host organisms, can cross the barrier of natural species, and put genes from any organism into new organisms, which can be independent of the original organisms. This ability is the first important feature of genetic engineering. The second feature is that a small DNA fragment is amplified in a new host cell, so that a small number of DNA samples can "copy" a large number of DNA, and a large number of absolutely pure DNA molecular groups are not polluted by any other DNA sequences. Scientists call the technology of changing the DNA of human germ cells "germ cell therapy", while the so-called "genetic engineering" is aimed at changing the germ cells of animals and plants. No matter what the name is, changing the DNA of an individual's germ cells is likely to produce the same changes to its offspring.
So far, genetic engineering has not been used in human body, but it has been tested on almost all non-human life forms, from bacteria to livestock, and achieved success. In fact, all insulin used to treat diabetes comes from a bacterium, and its DNA is inserted into the gene that can produce insulin by human beings, so that bacteria can replicate insulin by themselves. Genetic engineering technology enables many plants to resist pests and weeds; In the United States, about half of soybeans and a quarter of corn are genetically modified. At present, whether genetically modified animals and plants should be used in agriculture has become the focus of debate: supporters believe that genetically modified agricultural products are easier to grow and contain more nutrients (even drugs), which will help alleviate famine and diseases around the world; Opponents believe that introducing new genes into agricultural products will have side effects, especially damaging the environment.
It is true that there are still many genes whose functions and ways of interaction are unknown to human beings. However, considering that genetic engineering can make tomatoes have anti-cancer effect, make salmon grow several times larger than nature, and make pets no longer cause allergies, many people hope to make similar modifications to human genes. After all, embryo genetic disease screening, gene repair and genetic engineering can not only be used to treat diseases, but also make it possible to change other human characteristics such as eye color and intelligence. At present, we are far from designing and customizing our offspring, but there have been examples of cultivating people's physical characteristics with the help of embryonic genetic disease screening technology. For example, with this technology, parents of children can have a child whose bone marrow matches their children, and then the child can be cured by bone marrow transplantation.
With the secrets of the internal structure and genetic mechanism of DNA presented to people bit by bit, especially when people know that the genetic code is transcribed and expressed by RNA, biologists are no longer satisfied with exploring and prompting the secrets of biological inheritance, but are eager to try and imagine interfering with the genetic characteristics of organisms at the molecular level. If the genetic code fragment in one organism's DNA is connected to another organism's DNA chain and the DNA is recombined, new genetic material can be designed and new biological types can be created according to human wishes, which is completely different from the traditional practice of cultivating biological offspring in the past. This approach is like engineering design of technical science. According to human needs, this "gene" of this creature and that "gene" of that creature are reconstructed and assembled into a new gene combination to create a new creature. This kind of biological science and technology, which is carried out completely according to people's wishes, is called "genetic engineering" or "genetic engineering"
Basic operation steps of genetic engineering
1. Obtaining the target gene is the first step of genetic engineering.
2. The construction of gene expression vector is the second step and the core of genetic engineering.
3. Introducing the target gene into the recipient cell is the third step of genetic engineering.
4. Whether the target gene can stably maintain and express its genetic characteristics after being introduced into recipient cells can only be known through detection and identification. This is the fourth step of genetic engineering.
The prospect of genetic engineering The scientific community predicts that 2 1 century will be the century of genetic engineering. Genetic engineering is an artificial intervention in biological inheritance at the molecular level. To understand it, let's start with bioengineering: bioengineering, also known as biotechnology, is a comprehensive engineering technology that uses modern life science principles and technologies such as information and chemical engineering to process cheap raw materials to varying degrees and provide a large number of useful products by using living cells or enzymes produced by them.
The basis of bioengineering is modern life science, technology science and information science. The main products of bioengineering are to provide a large number of high-quality fermented products, such as biochemical drugs, chemical raw materials, energy, biological control agents, food and beverage, etc., and also provide social services for human beings such as environmental management, metal extraction, clinical diagnosis, gene therapy and crop variety improvement.
Bioengineering consists of five parts: genetic engineering, cell engineering, enzyme engineering, protein engineering and microbial engineering. Among them, genetic engineering is that people transform biological genes and use biology to produce special products that people want. With the secrets of the internal structure and genetic mechanism of DNA presented to people bit by bit, biologists are no longer satisfied with exploring and prompting the secrets of biological inheritance, but are eager to try and imagine interfering with the genetic characteristics of organisms at the molecular level.
Gilbert of America is the founder of base arrangement analysis. He took the lead in supporting the human genome project. If a genetic code fragment in one organism's DNA is connected to another organism's DNA chain and the DNA is recombined, can't we design new genetic material and create new biological types according to human wishes? This is completely different from the traditional practice of breeding biological offspring in the past. It is very similar to the engineering design of technical science, that is, according to human needs, this "gene" of this creature and that "gene" of that creature are reconstructed and assembled into a new gene combination to create a new creature. This kind of biological science and technology, which is carried out completely according to people's wishes, is called "genetic engineering" or "genetic engineering"
What is the main course of human genetic engineering? 1866, Austrian geneticist Father Mendel discovered the genetic law of living things. 1868, Swiss biologist Friedrich discovered that the nucleus has two parts: acidity and protein. The acidic part was later called DNA；; 1882, when German embryologist Walter Fleming studied salamander cells, he found that the nucleus contained a large number of divided linear objects, that is, later chromosomes. 1944, American researchers proved that DNA is the genetic material of most organisms, not protein; 1953, American biochemist Watson and British physicist Crick announced the discovery of the double helix of DNA, which laid the foundation of genetic engineering. 1980, the first transgenic mouse was born; 1996, the first cloned sheep was born; 1999, American scientists cracked the sequence map of the 22nd human genome. The future plan is to prescribe drugs for related diseases according to the genetic map.
Human genome research is the basic research of life science. Some scientists regard genome map as a road map or periodic table in chemistry; Some scientists compare the genome map to a dictionary, but from any angle, in order to promote human health, prevent diseases and prolong life, the application prospect of decoding and deciphering human genetic code is extremely beautiful. After the information of 65,438+10,000 human genes and their corresponding chromosome positions was deciphered, the genetic codes of human beings, animals and plants were deciphered, which opened up broad prospects for overcoming diseases and improving crop yield. It will become the source of knowledge and technological innovation in the pharmaceutical and biopharmaceutical industries. Beckwitz of the United States is observing colonies in a vessel. He once warned about the human genome project.
Scientific research has proved that some major diseases that plague human health, such as cardiovascular and cerebrovascular diseases, diabetes, liver diseases and cancer, are all related to genes. According to the decoded gene sequence and function, we can find out these genes, screen drugs according to the corresponding pathological positions, and even design new drugs according to the existing genetic knowledge, so as to repair or replace these pathological genes and cure persistent diseases. Gene medicine will become a dazzling star in the medical field in 2 1 century. Genetic research can not only provide basic data for screening and developing new drugs, but also provide the possibility for using genes to detect, prevent and treat diseases. For example, people with the same living habits and living environment have different susceptibility to the same disease due to different gene sequences. An obvious example is that some smokers are prone to lung cancer, while others are not. Doctors will give different guidance according to different gene sequences of different people, so that they can develop scientific and reasonable living habits and prevent diseases as much as possible.
With the development of human genetic engineering, decoding all human DNA is just around the corner.
The development of information technology has changed people's life style, and the breakthrough of genetic engineering will help people prolong their life. At present, the average life expectancy in some countries has exceeded 80 years, and China has also exceeded 70 years. Some scientists predict that with the effective treatment of chronic diseases such as cancer, cardiovascular and cerebrovascular diseases, there may be countries with an average life expectancy of more than 1000 years from 2020 to 2030. By 2050, the average life expectancy of human beings will reach 90 to 95 years.
Man will challenge the limits of life science. 1953 One day in February, British scientist francis crick announced that we had discovered the secret of life. He found that DNA is a double helix molecule existing in the nucleus, which determines the inheritance of organisms. Interestingly, the scientist announced this important scientific discovery in a bar in Cambridge. Deciphering the genetic codes of humans, animals and plants has opened up broad prospects for overcoming diseases and increasing crop yield. From 65438 to 0987, American scientists put forward the "Human Genome Project", whose goal is to determine all the genetic information of human beings, determine the specific positions of human genes on 23 pairs of chromosomes, find out the nucleotide sequence of each gene, and establish a human gene bank. 1999, the genetic code of human chromosome 22 was deciphered, and the "Human Genome Project" took a successful step. It can be predicted that in the next quarter century, scientists may reveal about 5,000 pathogenic genes of human genetic diseases, so as to find gene therapy for fatal diseases such as cancer, diabetes, heart disease and hemophilia.
Following the publication of the "working frame map" of the human genome by scientists on June 26th, 2000, scientists from China, the United States, Japan, Germany, France and Britain and Celera Company of the United States jointly published the human genome map and preliminary analysis results on February 2nd, 2006. The human genome map published this time is more accurate, clear and complete on the basis of the original "working frame map" after sorting, classification and arrangement. The human genome contains most of the genetic information of human birth, aging, disease and death. Deciphering it will bring a revolution to the diagnosis of diseases, the development of new drugs and the exploration of new treatments. The publication of human genome map and preliminary analysis results will play an important role in promoting the development of life science and biotechnology. With the further development of human genome research, life science and biotechnology will enter a new era with the new century.
There are at least two strong proofs that genetic engineering has made great progress in the 20th century. One is genetically modified animals and plants, and the other is cloning technology. Transgenic animals and plants have been implanted with new genes, which makes them have brand-new characters that they did not have before, thus causing an agricultural revolution. Now transgenic technology has been widely used, such as insect-resistant tomatoes and fast-growing crucian carp. The birth of cloned sheep was the first of the top ten scientific and technological breakthroughs in the world in 1997. This ewe named Dolly is the first mammal produced by asexual reproduction, and it completely inherits the genetic genes of the ewe that gave it the nucleus. "Cloning" has become the focus of people's attention for a time. Although there are ethical and social problems, the great progress of biotechnology has given mankind a broader imagination space for the future.
Memorabilia of genetic engineering
From 1860 to 1870, Austrian scholar Mendel put forward the concept of genetic factor according to pea hybridization experiment and summarized Mendel's genetic law.
1909, Danish botanist and geneticist Johnson first put forward the word "gene" to express Mendel's concept of genetic factors.
1944, three American scientists isolated bacterial DNA (deoxyribonucleic acid) and found that DNA is a molecule carrying the genetic material of life.
1953, American Watson and Englishman Crick put forward the double helix model of DNA molecules through experiments.
1969 Scientists successfully isolated the first gene.
1980, scientists cultivated the world's first transgenic animal transgenic mouse for the first time.
1983, scientists cultivated the world's first transgenic plant transgenic tobacco for the first time.
1988 K.Mullis invented PCR technology.
1990 10 The International Human Genome Project, known as the Apollo Moon Landing Program in life science, was launched.
From 65438 to 0998, a group of scientists founded Celera Gene Company in Rockwell, USA, to compete with the International Human Genome Project.
1998 12 the complete genome sequence of a small nematode has been determined, which is the first time that scientists have drawn the genome map of a multicellular animal.
1In September 1999, China was allowed to join the Human Genome Project and was responsible for determining 1% of the total sequence of the human genome. China is the sixth country to participate in the international human genome project after the United States, Britain, Japan, Germany and France, and it is also the only developing country to participate in this project.
1 99965438+February1day, the joint research team of the International Human Genome Project announced that the genetic code of the 22nd human chromosome has been completely decoded, which is the first time that humans have successfully completed the determination of the complete gene sequence of the human chromosome.
On April 6, 2000, Celera announced that it had cracked the complete genetic code of an experimenter, but it was questioned by many scientists.
At the end of April 2000, Chinese scientists completed the working framework of 1% human genome according to the deployment of the International Human Genome Project.
On May 8, 2000, German and Japanese scientists announced that the sequencing of chromosome 2 1 had been basically completed.
On June 26th, 2000, scientists published the working draft of human genome, which marked an important step for human beings to interpret their "book of life".
In June 5438+February 65438+April 2000, scientists in the United States and Britain announced that they had drawn a complete map of Arabidopsis genome, which was the first time that human beings had completely deciphered the gene sequence of a plant.
2001February 12 Chinese, American, Japanese, German, French and British scientists jointly published the human genome map and preliminary analysis results.
For the first time, scientists published the draft of "genetic information" of the human genome.
[Edit this paragraph] Gene research countries are competing for the global map of the gene age.
Let's take a look at the research on genetic science in countries around the world at the arrival of the new century.
Britain: As early as the mid-1980s, Britain had its first biotechnology enterprise, which was the earliest among European countries. Today, it has 560 biotechnology companies, and Britain accounts for half of the 70 listed biotechnology companies in Europe.
Germany: Recognizing that biotechnology will be the key to maintain Germany's future economic competitiveness, the German government passed legislation in 1993 to simplify the examination and approval procedures for biotechnology enterprises, and allocated1500,000 Deutsche Mark to set up three biotechnology research centers. In addition, the government also plans to spend 654.38+0.2 billion marks on the research of the human genome project in the next five years. 1999, German researchers applied for biotechnology patents, accounting for 14% in Europe.
France: In the past 10 years, the French government's funds for biotechnology have increased by 10 times. The most typical project is the so-called "Gene Valley" Science Park established by 1998 near Paris, where the most promising emerging biotechnology companies in France gather. Another 20 French cities are also planning to set up their own biotechnology parks in imitation of the "Gene Valley".
Spain: Mar Pharmaceutical Company is the representative of this country's biotechnology enterprises, specializing in finding anticancer substances from marine life. Among them, ET-743 is the most valuable one, which is a red anticancer drug extracted from the seabed ejecta in the Caribbean and Mediterranean. ET-743 is planned to be registered and produced in Europe in 2002, and will be used to treat common cancers such as bone cancer, skin cancer, ovarian cancer and breast cancer.
India: The Indian government funds more than 50 research centers across the country to collect human genome data. Due to the unique "caste system" and the intermarriage customs of some remote tribes, the gene bank of Indian population is the most complete in the world, and it is a very valuable database for scientists to find the pathology and treatment of genetic diseases. However, private biotechnology enterprises in India are still in their infancy.
Japan: The Japanese government plans to increase the funding for biotechnology research by 23% next year. A private company has also established the Dragon Gene Center, which will be the largest genome research institution in Asia.
Singapore: Singapore announced a $60 million genetic technology research project to study how diseases have different effects on Asians and whites. The plan focuses on analyzing genetic differences and what treatment methods are effective for Asians, so as to finally gain new knowledge of identifying and treating diseases; And set up high-tech companies to manufacture drugs and medical products derived from this research.
China: Participated in the Human Genome Project and determined the sequence of 1%, which brought a bright future to the bio-industry in China in the 2nd1century. This "1% project" has enabled China to enter the international advanced ranks of bio-industry, and also enabled China to naturally share all the achievements, resources and technologies of the Human Genome Project.
[Edit this paragraph] Genetic Engineering and Agriculture, Animal Husbandry and Food Industry
Using genetic engineering technology, we can not only cultivate high-quality, high-yield and disease-resistant crops and new varieties of livestock and poultry, but also cultivate animals and plants with special uses.
1. Transgenic fish
Transgenic fish with fast growth, tolerance to harsh environment and good meat quality (China).
2. Transgenic cattle
Transgenic cattle with human growth hormone in milk (Argentina).
3. Transgenic sweet pepper with cucumber bacterial wilt resistance gene
4. Tomato with fish cold-resistant gene
5. Transgenic potato with cucumber bacterial wilt resistance gene
6. Genetically modified soybeans that will not cause allergies
7. Superanimals
Super sheep and super mouse with storage protein gene introduced
8. Special animals
Pigs and mice with special uses by introducing human genes.
9. Insect resistant cotton
Bacillus thuringiensis can synthesize toxic protein to kill cotton bollworm. Insect-resistant cotton can be obtained by introducing the gene into cotton cells in vitro and then conducting tissue culture.
[Edit this paragraph] Genetic engineering and environmental protection
The DNA probe made by genetic engineering can detect viruses, bacteria and other pollution in the environment very sensitively.
Indicator organisms cultivated by genetic engineering can reflect environmental pollution very sensitively, but they are not easy to die in large numbers because of environmental pollution, and can even absorb and transform pollutants.
Genetic engineering and environmental pollution control
The "super bacteria" produced by genetic engineering can devour and decompose a variety of substances that pollute the environment.
Usually, a bacterium can only decompose one hydrocarbon in oil, but the "super bacteria" successfully cultivated through genetic engineering can decompose many hydrocarbons in oil. Some can also swallow and transform heavy metals such as mercury and cadmium and decompose toxic substances such as DDT. )
[Edit this paragraph] Gene therapy can wait for the medical revolution.
"Gene" means the word "gene" that we often see now, which is the most basic factor that determines all life phenomena of a biological species. Scientists believe that the translation of this word is not only fluent in sound, but also appropriate in meaning, and it is a model of foreign language translation of scientific terms. As the genetic unit in the body, genes can not only determine our appearance and height, but also lead to various diseases. Some defective genes may be passed on to future generations, while others will not. Gene therapy was originally proposed for genetic diseases with single gene defect, aiming at replacing the defective gene with a normal gene or remedying the pathogenic factors of the defective gene.
Using genes to treat diseases is to introduce functional genes into patients for expression. The disease can be treated because the expression product-protein has played a role. The result of gene therapy is like an operation on a gene, which can cure the disease and remove the roots, so some people describe it as "molecular surgery".
We can divide gene therapy into two types: sex cell gene therapy and somatic cell gene therapy. Sex cell gene therapy is to operate in patients' sex cells so that their offspring will never get this genetic disease again. Somatic gene therapy is the mainstream of gene therapy research at present. However, its shortcomings are also obvious. It has not changed the genetic background of patients with single or multiple genetic defects, so that some people's offspring will inevitably suffer from this disease.
No matter what kind of gene therapy is in the initial stage of clinical trial, it has no stable curative effect and complete safety, which is the current research status of gene therapy.
It can be said that it is quite dangerous to carry out gene therapy before fully explaining the operating mechanism of the human genome and fully understanding the gene regulation mechanism and the molecular mechanism of diseases. It is particularly important to enhance the safety of gene therapy and improve the rigor and rationality of clinical trials. Although there are still many obstacles to overcome in gene therapy, the general trend is encouraging. According to statistics, as of the end of 1998, 373 clinical bills have been implemented in the world, and 3 134 people have accepted gene transfer experiments, which fully shows its great development potential and application prospect. As predicted by the founder of gene therapy, the emergence of gene therapy will promote the revolutionary changes in medicine in the new century.
[Edit this paragraph] Genetic engineering has brought Chinese medicine into a new era.
China expert 65438+65438, who attended the international symposium on "Traditional Chinese Medicine and Natural Medicine" on May 3rd, thinks that the research on transgenic medicinal plants or organs, the cloning of key enzyme genes of effective secondary metabolism pathway, the molecular markers of traditional Chinese medicine and the research on gene chip of traditional Chinese medicine have become the hot spots in the research of traditional Chinese medicine, which will bring traditional Chinese medicine into a brand-new era.
According to Guo De 'an, deputy director of the State Key Laboratory of Natural Medicine and Biomimetic Medicine in Peking University, the research on transgenic medicinal plants or organs and tissues is one of the more active fields in biotechnology of traditional Chinese medicine in recent years.
In the research of transgenic medicinal plants, the Institute of Medicinal Plants of China Academy of Medical Sciences used Agrobacterium rhizogenes and Agrobacterium tumefaciens to induce Salvia miltiorrhiza to form hairy roots and crown gall, and then differentiated into plants. They made a comparative study on the morphology and chemical composition between them and cultivated salvia miltiorrhiza. The results showed that the leaves of plants regenerated from hairy roots were shriveled, internodes were shortened, plants were dwarfed and fibrous roots were developed. However, the crown gall tissue regenerated plants have tall plant type, developed root system, high yield and higher tanshinone content than the control, which is of great significance for salvia miltiorrhiza breeding and improving the quality of medicinal materials.
Guo Dean said that studying the biosynthetic pathway of chemical components of traditional Chinese medicine not only contributes to the bionic synthesis of these chemical components, but also can artificially regulate the synthesis of these chemical components, which is conducive to the directional synthesis of the required chemical components. Domestic research in this field has begun.
It is understood that the application research of biotechnology in Chinese medicine research is gradually emerging. Some aspects, such as tissue and cell culture of medicinal plants, have accumulated 20 or 30 years of experience, and the theory and technology are quite mature, which has formed a certain scale in the country. Among them, the research on cell engineering of Chinese herbal medicine is in its heyday.
Guo Dean said that in the face of the problem that many wild plants are on the verge of extinction and it is difficult to introduce in some special environments, Chinese scientists have begun to explore the production of useful secondary metabolites by cultivating a large number of higher plant cells and organs. The research contents include the screening of high-yield tissues or cell lines, the optimization of culture conditions and the regulation of biosynthesis pathway of secondary metabolites in order to reduce costs and improve the yield of secondary metabolites.
In addition, the research on biotransformation of exogenous chemical components by using plant suspension cultured cells or adventitious roots and hairy roots has also quietly emerged in recent years, and has made some progress.
Moreover, scientists pay more attention to the regulation of biosynthesis pathway of secondary metabolites. These studies have achieved exciting results, indicating that the cell culture of medicinal plants in China has entered a new era.