Cloning is a transliteration of English clone, which is simply an artificially induced asexual reproduction method. But cloning is different from asexual reproduction. Asexual reproduction means that there is no combination of male and female germ cells, and only one kind of organism produces offspring. The common reproduction methods are spore reproduction, budding reproduction and fission reproduction. It is also called asexual reproduction to produce new individuals by layering or grafting the roots, stems and leaves of plants. Sheep, monkeys, cows and other animals cannot reproduce asexually without manual operation. Scientists call the process of artificial gene manipulating animal reproduction cloning, and this biotechnology is called cloning technology.
The basic process of cloning is to transplant the nucleus of a donor cell containing genetic material into an egg cell without nucleus, then fuse the two cells into one by micro-current stimulation, and then promote the new cells to divide and reproduce and develop into embryos. When the embryo develops to a certain extent, it is implanted into the uterus of an animal to make the animal pregnant, and then an animal with the same gene as the cell donor can be born. In this process, if the donor cells are genetically modified, the genes of the offspring of asexual animals will also change in the same way.
Cloning technology does not require male and female mating, and does not require the combination of sperm and eggs. It only needs to extract single cells from animals, cultivate them into embryos by artificial methods, and then implant the embryos into female animals to breed new individuals. This cloned animal cultured with single cells has exactly the same characteristics as the single-cell donor and is a "replica" of the single-cell donor. Scientists in Britain and Oregon in the United States have successively cultivated "cloned sheep" and "cloned monkeys". The success of cloning technology is called "historic event and scientific innovation". Some people even think that cloning technology can be compared with the advent of the atomic bomb that year.
Cloning technology can be used to produce "cloned human" and "cloned human", which has aroused widespread concern all over the world. Is cloning sad or happy, a curse or a blessing for human beings? Materialist dialectics holds that everything in the world is a contradictory unity, which is divided into two parts. So is cloning technology. If we use cloning technology to "copy" a war madman like Hitler, what will it bring to human society? Even if it is used to "copy" ordinary people, it will bring a series of ethical problems. If cloning technology is applied to animal husbandry production, it will make fundamental changes in the cultivation and reproduction of excellent livestock breeds. If cloning technology is used in the research of gene therapy, it is very possible to overcome the persistent diseases that endanger human life and health, such as cancer and AIDS. Cloning technology, like atomic energy technology, is a double-edged sword with the hilt in human hands. Human beings should take joint action to avoid the emergence of "human cloning" and let cloning technology benefit human society.
Research status of cloning technology
First, the early research of cloning.
The word clone is a transliteration of the English word clone. As a noun, c 1one is usually translated as asexual clone. The genetic composition of all members in the same clone is exactly the same, unless there is mutation. Cloning of natural plants, animals and microorganisms has long existed in nature. For example, identical twins are actually clones. However, natural mammals have a very low incidence of cloning, a small number of members (generally two), lack of purpose, and are rarely used to benefit mankind. Therefore, people began to explore artificial methods to produce higher animal clones. In this way, the word cloning began to be used as a verb to refer to the behavior of artificially cultivating cloned animals.
At present, there are two main methods to produce mammalian clones: embryo segmentation and nuclear transfer. Dolly, a cloned sheep cultivated by scientists from various countries, and various cloned animals later adopted nuclear transplantation technology. The so-called nuclear transfer refers to the process of transplanting the nuclei of embryos or adult animals at different development stages into enucleated oocytes through microsurgery and cell fusion, re-forming embryos and making them mature. Different from embryo segmentation technology, nuclear transfer technology, especially continuous nuclear transfer technology, can produce an infinite number of genetically identical individuals. Because nuclear transfer is an effective method to produce cloned animals, people usually call it animal cloning technology.
The idea of cloning animals by nuclear transplantation was first put forward by Hans Spearman in 1938. He called it a "strange experiment", that is, taking out the nucleus from a developing embryo (mature or immature embryo) and transplanting it into an egg. This idea is the basic way to clone animals now.
Starting from 1952, scientists first carried out nuclear transfer cloning experiments with frogs, and successively obtained tadpoles and adult frogs. From 65438 to 0963, the scientific research group led by Professor Tong Dizhou in China studied the nuclear transfer technology of fish embryos for the first time, and achieved success.
The first achievement of mammalian embryo nuclear transfer research was obtained in 198 1 year-Karl Ilmen Ze and Peter Hope used mouse embryonic cells to culture normal mice. 1984, Steen Willadsen cloned a live-born sheep with immature embryo cells from sheep. Later, some people repeated his experimental method with various animals such as cattle, pigs, goats, rabbits and macaques. 1989, Willadson obtained the second generation of cloned cattle with continuous nuclear transfer. In 1994, Neil Fierst cloned a cow from a late embryo with at least 120 cells. By 1995, nuclear transfer of major mammalian embryos was successful, including frozen and in vitro embryos; Nuclear transplantation experiments of embryonic stem cells or adult stem cells have also been tried. However, until 1995, the transfer of differentiated nuclei in adult animals has not been successful.
Second, the significance and response of Dolly's cloned sheep
The above facts show that before1February 1997, the research group of Dr. Wilmut of Roslin Institute announced the successful cultivation of somatic cloned sheep Dolly, the embryo nuclear transfer technology had made great progress. In fact, the cloned Dolly followed the whole process of embryo nuclear transfer in nuclear transfer technology, but this can not reduce Dolly's significance, because it is the first animal born by somatic cell nuclear transfer in the world, which is a major breakthrough in the field of cloning technology. This great progress means: it is proved theoretically that the differentiated animal nucleus is totipotent, just like plant cells, the genetic material in the nucleus will not change irreversibly during differentiation; Practice has proved that the technology of animal cloning with somatic cells is feasible, and countless identical cells can be used as donors for nuclear transfer, and a series of complex genetic operations can be carried out on these donor cells before they are fused with egg cells, thus providing an effective method for breeding excellent animal varieties and mass production of transgenic animals.
In theory, using the same method, people can copy "human cloning", which means it is entirely possible for dictators in science fiction to clone themselves. Therefore, the birth of "Dolly" has aroused strong repercussions in the scientific, political and even religious circles all over the world, and triggered a discussion on the moral issues derived from human cloning. Governments and people all over the world have reacted: cloning human beings is against ethics. Nevertheless, the great theoretical significance and practical value of cloning technology have prompted scientists to speed up their research, thus pushing the research and development of animal cloning technology to a climax.
Three, the important achievements of cloning research in recent three years
The birth of Dolly, a cloned sheep, set off an upsurge of cloning research all over the world. Subsequently, reports on cloned animals continued. 1 in March, 997, that is,1month after Dolly was born, scientists from the United States, China, Taiwan Province Province of China and Australia respectively announced that they had successfully cloned monkeys, pigs and cows. But all of them are cloned with embryonic cells, and the significance can't be compared with Dolly. In July of the same year, Roslin Institute and PPL announced that Polly, the world's first transgenic sheep with human genes, had been cloned from transgenic fetal fibroblasts. This achievement shows the great application value of cloning technology in cultivating transgenic animals.
In July, 1998, Wakayama, University of Hawaii reported that 27 surviving mice were cloned from mouse cumulus cells, of which 7 were only the offspring of cloned mice, which was the second batch of mammalian somatic cell nuclear transfer offspring after Dolly. In addition, Wakayama and others adopted a relatively simple and high success rate new cloning technology, which was different from Dolly's, and named it "Honolulu Technology" after the location of the university.
Since then, scientists from the United States, France, the Netherlands and South Korea have also reported the success of somatic cell cloning cattle. The research enthusiasm of Japanese scientists is particularly amazing. July 1998 to April 1999, Tokyo Agricultural University, Feng Jingen University, livestock improvement enterprise group, local livestock test sites (Ishikawa Prefecture, Oita Prefecture, Kagoshima Prefecture, etc.) and private enterprises (such as Yin Xue Dairy, the largest dairy company in Japan, etc.). It is reported that they use bovine ear and hip muscles. By the end of 1999, somatic cloned offspring of six types of cells-fetal fibroblasts, breast cells, cumulus cells, oviduct/uterine epithelial cells, muscle cells and ear skin cells-had been successfully born in the world.
In June, 2000, China Northwest A&F University cloned two "cloned sheep" from adult goat somatic cells, but one of them died of respiratory system dysplasia. According to reports, the cloning technology adopted by the research team is completely different from Dolly's, which shows that scientists in China have also mastered the cutting-edge technology of somatic cell cloning.
Nuclear transplantation experiments between different species have also achieved some gratifying results. 1998, 1 In June, scientists at the University of Wisconsin-Madison in the United States successfully cloned the embryos of five mammals: pigs, cows, sheep, rats and macaques. The results show that the unfertilized eggs of a species can combine with the mature nuclei of many animals. Although these embryos miscarried, it made a useful attempt to the possibility of heterogeneous cloning. 1999, American scientists cloned the embryo of a rare animal argali from cow eggs. Scientists in China have also cloned early embryos of giant pandas from rabbit eggs, which indicates that cloning technology may become a new way to protect and save endangered animals.
Fourth, the application prospect of cloning technology
Cloning technology has shown broad application prospects, which can be summarized in the following four aspects: (1) cultivating excellent varieties and producing experimental animals; (2) producing transgenic animals; (3) producing human embryonic stem cells for cell and tissue replacement therapy; (4) reproduction of endangered animal species, preservation and dissemination of animal species resources. The production of transgenic animals and embryonic stem cells is briefly described as follows.
The research on transgenic animals is one of the most attractive and promising topics in the field of animal bioengineering. Transgenic animals can be used as donors for medical organ transplantation, as bioreactors, as well as for genetic improvement of livestock and the establishment of experimental models of diseases. However, there are not many practical applications of transgenic animals at present. In addition to the medical model of transgenic mice modified by a single gene, the research on the production of drug proteins by mammary gland bioreactor of transgenic animals has been going on for a long time, which has been more than 10 years. But at present, only two drugs in the world have entered the phase III clinical trial, and 5 ~ 6 drugs have entered the phase II clinical trial. However, transgenic livestock strains whose agronomic traits have been improved and can be used for livestock production have not yet been born. The low production efficiency of transgenic animals, the high cost and regulation failure caused by the difficulty of fixed-point integration, and the separation of genetic characters of sexually propagated offspring of transgenic animals, which are difficult to maintain the excellent victory of ancestors, are the main reasons that restrict the practical process of transgenic animals today.
The success of somatic cell cloning has set off a new revolution for the production of transgenic animals, and animal somatic cell cloning technology provides a technical possibility for rapidly amplifying the germplasm innovation effect produced by transgenic animals. Using simple somatic cell transfection technology to transfer the target gene can avoid the difficulty and inefficiency of livestock germ cells. At the same time, the transgenic cell line can be used for pre-inspection of transgenic integration and gender pre-selection under laboratory conditions. Before nuclear transfer, the fusion gene of target exogenous gene and marker gene (such as LagZ gene and neomycin antibiotic gene) was introduced into cultured somatic cells, and then transgenic positive cells and their clones were screened through the expression of marker genes, and then the nucleus of the positive cells was transplanted into enucleated oocytes. Theoretically, the final animal should be a 100% positive transgenic animal. By this method, Schnieke et al. (Bio Report, 1997) have successfully obtained 6 transgenic sheep, of which 3 have human coagulation factor IX gene and marker gene (neomycin resistance gene), and 3 have marker gene, and the integration rate of target foreign gene is as high as 50%. Cibelli (Science, 1997) also obtained three transgenic cows by nuclear transfer, which confirmed the effectiveness of this method. It can be seen that one of the most important application directions of animal cloning technology today is to develop transgenic cloned animals with high added value.
Embryonic stem cells are totipotent stem cells and have the potential to form all adult cell types. Scientists have been trying to induce various stem cells to differentiate into specific tissue types to replace those damaged tissues in the body, such as implanting insulin-producing cells into diabetic patients. Scientists have been able to transform pig es cells into beating cardiac myocytes, human ES cells into nerve cells and mesenchymal cells, and mouse ES cells into endodermal cells. These results open the way for cell and tissue replacement therapy. At present, scientists have successfully isolated human es cells (Thomson et al. 1998, Science), and somatic cell cloning technology provides the possibility for producing patients' own ES cells. The patient's somatic cells were transplanted into enucleated oocytes to form recombinant embryos, which were cultured into blastocysts in vitro. Then es cells were isolated from blastocysts and differentiated into specific cell types (such as nerve cells, muscle cells and blood cells) for replacement therapy. The ultimate goal of this nuclear transplantation method is to treat stem cells, not to obtain cloned individuals, which scientists call "therapeutic cloning".
The application of cloning technology in basic research is also very significant, which provides a tool for studying the mechanisms of gamete and embryogenesis, cell and tissue differentiation, gene expression regulation, nuclear-cytoplasmic interaction and so on.
Problems in verb (verb abbreviation) cloning technology
Although cloning technology has broad application prospects, it is still far from industrialization. As a new research field, cloning technology is not mature in theory and technology. Theoretically, the mechanism of reprogramming genetic material through differentiated somatic cell cloning (the process in which all or most genes in the nucleus are turned off and cells regain totipotency) is still unclear. Whether cloned animals will remember the age of donor cells, whether the continuous offspring of cloned animals will accumulate mutant genes, and the genetic role played by cytoplasmic mitochondria in the cloning process have not been solved.
In practice, the success rate of cloning animals is still very low. In the experiment of cultivating Dolly, Wilmut's research team fused 277 eggs with the transplanted nucleus, and only one live sheep Dolly was obtained, with a success rate of only 0.36%. At the same time, the cloning success rates of embryonic fibroblasts and embryonic cells were only 65,438 0.7% and 65,438 0.5%, respectively. 36866.88868688666
In addition, some born individuals show physiological or immune defects. Taking cloned cattle as an example, many cloned cattle cultivated in Japan, France and other countries died within two months after birth; By February 2000, 12 1 somatic cloned cattle had been born in Japan, but only 64 cows survived. The results showed that the placental function of some calves was not perfect, and the oxygen content and growth factor concentration in blood were lower than the normal level. The thymus, spleen and lymph glands of some calves are abnormal; Fetuses of cloned animals generally tend to develop faster than ordinary animals, which may be the cause of death.
Even Dolly, who developed normally, was found to have signs of premature aging. The end of the chromosome is called telomere, which determines the number of times a cell can divide: every time it divides, the telomere will be shortened, and when the telomere is exhausted, the cell will lose its ability to divide. 1998, scientists found that Dolly's cell telomeres are shorter than those of normal people, that is, its cells are in a more aging state. At that time, it was thought that this might be caused by the cloning of Dolly from adult sheep cells, which made its cells bear the imprint of adult cells. However, this explanation is now questioned. Robert Lanza, a doctor in Massachusetts, USA, cloned cattle from cultured aging cells and got six calves. After 5 ~ 10 months of birth, it was found that the telomeres of these cloned cows were longer than those of ordinary calves of the same age, and some even longer than those of ordinary newborn calves. At present, it is not clear why this phenomenon is different from Dolly's. However, this experiment shows that in some cases, the cloning process can change the molecular clock of mature cells and make them "rejuvenate". The effect of this change on the life span of cloned animals needs further observation.
In addition to the above theoretical and technical obstacles, the ethical impact of cloning technology (especially its application in human embryos) and the strong public reaction to it also limit its application. However, the development of cloning technology in recent years shows that most countries in the world are unwilling to lag behind, and no one has given up the research on cloning technology. At this point, the attitude of the British government is very representative. Less than 1 month after the end of February 1997, the British Science and Technology Council published a special report on cloning technology, indicating that the British government would reconsider this decision and think it unwise to ban this research blindly. The key is to establish certain norms and use them to benefit mankind.
Respondent: Governor ☆ Governor-probation period 1 grade 3-7 20:59.
I. The concept of cloning
As we all know, the reproduction of living things is accomplished through reproduction. There are two ways of biological reproduction: one is called sexual reproduction and the other is called asexual reproduction.
Sexual reproduction is a reproductive mode in which bisexual germ cells (sperm and eggs) fuse and develop into offspring. Asexual reproduction does not combine hermaphroditic germ cells, but forms individuals through the division and reproduction of the organism itself or the growth and development of its somatic cells. Asexual reproduction is common in plants and some animals (such as single-celled animals and lower animals).
Cloning is a transliteration of the English word "clone", which comes from the Greek word klon, meaning seedling or twig, and refers to some plants that reproduce asexually or nutritionally. With the passage of time and the development of science, its meaning has increased a lot, such as a group of cells produced by a cell in vitro culture; DNA sequences produced by "parent" sequences, and so on. In a word, cloning refers to obtaining a group of cells or individuals with identical genes from a cell or individual through asexual reproduction.
The Monkey King in China's famous classic The Journey to the West can "transform" many the Monkey King as long as he pulls out a hair from his mouth and blows a fairy tale. Because pulling a finger on a finger will inevitably bring a group of cells, and this group of cells can cultivate a group of the same Sun Shengda. This is also asexual reproduction. It's just that Sun's skills are so high that he can "clone" thousands of himself in an instant. In short, cloning is asexual reproduction, that is, "replication" and "replication".
Second, plant cloning.
Asexual reproduction (cloning) is originally a low-level reproductive mode. The lower the level of biological evolution, the more likely it is to adopt this mode of reproduction, and the higher the level of evolution, the less likely it is to adopt this mode of reproduction. Because lower organisms, such as microorganisms, reproduce through self-division, and the genetic material of the offspring after division is exactly the same as their parents, in this sense, microorganisms have no "individuals" and they have not died. Although there are some differences between the parents and offspring of microorganisms in a strict sense, because their external nutritional environment will still be different, from the perspective of higher animals, this difference seems too insignificant. When this difference can be ignored, people can say that they are immortal to microorganisms. Death is the product of biological evolution to a higher stage. Normal cells or cancer cells cultured in vitro by cloning technology in biomedical research are also called "immortalized cell lines", that is, these cells are "immortal".
Biomedical research has entered the microscopic level. It is a very arduous task to cultivate immortal cell lines of normal or abnormal cells by cloning technology, but it has been paid more and more attention by scientific and medical circles in various countries. In agriculture, people have cultivated plants suitable for human needs by cutting and layering. In animal husbandry, countries are conducting research on cloning technology to produce more excellent animals. However, in higher organisms, the development from an adult somatic cell to an adult is a great development of cloning technology.
Many years ago, researchers at Cornell University in the United States stirred mature carrots at high speed to obtain single carrot cells, and then put these single cells into a growth medium to cultivate carrots with the same genes. This experiment confirmed the theory of plant cell totipotency. The so-called totipotency theory of plant cells means that every cell of plants, including somatic cells, has the potential to develop into a complete individual.
The theory of plant cell totipotency has been widely proved in the plant world. Now we can obtain a complete plant from any living cells, tissues and organs of plants by artificial culture in vitro, and produce many plants. This technique is called tissue culture. It has been used for industrialized production of test-tube seedlings of flowers and crops (such as sugarcane).
Third, the process of animal cloning.
The research of animal asexual reproduction has always been a subject explored by scientists. Because human beings have been cultivating livestock breeds through sexual reproduction for thousands of years, the result is that some excellent individuals or groups have been produced. They can meet people's needs and desires better than ordinary individuals. For example, a cow with a particularly high milk yield, a flock of sheep with a particularly high wool yield, an award-winning racehorse or an excellent police dog. However, the offspring who have sexual reproduction do not necessarily behave like their parents, and some even behave worse than their parents. The reason is that eggs or sperm only carry any half of the alleles that make up the parents, and the alleles can have almost unlimited combinations, so different offspring will be produced. There are great differences between brothers and sisters, because it is extremely difficult to have exactly the same genotype.
So it is difficult to maintain a phenotype through sexual reproduction. If an ideal phenotype is obtained, such as a cow with high milk yield, it is obviously valuable from an economic point of view to maintain, expand and reproduce this phenotype through asexual reproduction, that is, to produce many genetically identical individuals.
Egg cells are cultured into adults.
195 1 ~ 1959, Zhu Xian, a famous cell biologist in China, stimulated toad's egg cells with a glass needle with a diameter of 10 ~ 13um, and for the first time in the world, 25 adult toads, namely fatherless toads, were cultivated. They can live up to eight months.
Germ cells were used in the above experiments. Can animal bodies be obtained by culturing somatic cells? That is to say, plant cells are totipotent, and so are animal cells? There is no doubt that every animal cell, including somatic cells, has a complete set of genes of this species, but it has not been successful to culture somatic cells directly into animal adults. In order to prove that animal cells are totipotent, biologists have carried out a large number of nuclear transplantation experiments.
2. Nuclear transfer test
1939, scientists conducted the first nuclear transplantation experiment in amoeba. They transplanted the nucleus into the same kind of enucleated amoeba, and as a result, the recombinant amoeba could grow and reproduce.
Since 1963, Tong Dizhou, a famous biologist in China, has carried out a large number of nuclear transfer experiments in fish. 1980, they used carp blastocyst nucleus as donor nucleus and unfertilized mature eggs of crucian carp as recipient, and 2.7% of transplanted eggs developed into adult fish. The main characteristics of carp and crucian carp nuclear transfer fish are the same as those of carp, but the number of vertebrae is the same as that of crucian carp, and the number of lateral scales is between these two kinds of fish. The growth rate of this cell-engineered fish is 22% faster than that of carp, and it has been widely popularized in production.
1966, scientists conducted a nuclear transplantation experiment with the amphibian Xenopus laevis. They transferred the nuclei of tadpoles' intestinal cells into enucleated eggs, and as a result, 1.5% of the recombinant cells developed into adults. Their experiments proved for the first time that animal somatic cells are totipotent, but they have not been proved in mammalian somatic cells.
13. Cloning mammals with embryonic cells.
1986, British scientists used sheep 8-cell embryonic cells (cells before 8-cell embryos can show totipotency) as donor cells, and sheep egg cells as donor cells. As a result, the recombinant cells can develop into sheep adults, and then animals such as cattle, mice, rabbits and monkeys can be cloned from embryonic cells. It should be pointed out that this experiment is not to copy rams or ewes, but to copy their offspring, so there are still some shortcomings or defects in the experiment.
In China, mammals were cloned from embryonic cells, and in the late 1980s, they were cloned again. Sheep were cloned by Northwest Agricultural University and Jiangsu Agricultural College at 199 1. 1993, Institute of Development of China Academy of Sciences and Agricultural College of Yangzhou University cloned goats. 1995 south China normal university and Guangxi agricultural university cloned cattle. In addition, Hunan Medical College also cloned mice. However, cloning mammals from somatic cells other than embryonic cells was initiated by British scientist Wilmut.
Fourth, the birth of "Dolly"
"Dolly" is the first lamb in the world that was obtained by using somatic cells-mammary epithelial cells through nuclear transfer technology and complicated manual operation. The operation process is as follows:
1. Take out the egg from Scottish black-faced ewe (a kind of sheep) and suck the genetic material of the egg to make it into an egg with only cytoplasm.
Mammary epithelial cells were taken from ewes (B sheep) in the third trimester of pregnancy and cultured for 3-6 generations in vitro. These cells are treated with drugs to control their development and keep them at rest. This is a crucial step. Then resting cells are used as donor cells.
13. Introduce donor cells into the zona pellucida cavity of the egg. Then, donor cells and eggs are fused by electrical pulse stimulation to form reconstructed eggs.
The reconstructed egg was transplanted into the oviduct of a black-faced ewe (sheep C), and the oviduct of sheep C was ligated before, so that the embryo could not enter the uterus. C sheep play the role of cultivating embryos in vivo, which is called intermediate receptor.
Six days after the reconstructed eggs were transferred into the fallopian tube of C sheep, the embryos were washed out of the fallopian tube, and the embryos that developed normally to the morula stage and blastocyst stage were selected.
6. Transplant 1-3 morula or blastocyst into the uterus of Scottish black-faced sheep (Ding sheep). After the embryo was transplanted into the uterus, it continued to develop and finally gave birth to Dolly. This ewe is called "surrogate mother"
About 434 eggs were used in this project, and 277 reconstructed eggs were obtained. Six days after transplantation into the intermediate recipient, 247 embryos were rushed out, of which 29 (1 1.7%) developed into morula and blastocyst. Twenty-nine embryos were transferred to 13 surrogate mothers, and finally 1 Dolly was born, with a lambing rate of only 3.4%. If calculated by the number of reconstructed eggs, the lambing rate is less than 4 ‰. It can be seen that this technology needs to be improved. In addition, it should be noted that sheep cloning technology has not been completely replicated, and the cytoplasm of enucleated eggs will also contain a small amount of genetic material, which can also play an important or even decisive role in embryo development. The inheritance of organisms is the result of the interaction between nucleus and cytoplasm. Cytoplasmic genes are also DNA fragments, and their carriers are mainly some organelles, such as plastids and mitochondria. Cytoplasmic genes are independent to a certain extent and are generally not interfered by nuclear genes. Compared with nuclear genes, although the nucleus contains 99.9% genetic information, the expression of individual traits will still be affected by the cytoplasm of eggs. So theoretically, "Dolly" sheep is not a complete replica. Because "Dolly" is only a lonely one, some people think that the statement that "Dolly" is a cloned animal is not accurate. Although only 1 "Dolly" has been obtained so far, it is a great scientific achievement that attracts worldwide attention.
Significance and economic value of verb (verb abbreviation) cloning technology
The magnificent human history is largely driven by technology: metal manufacturing and improved agriculture have separated civilization from the Stone Age; /kloc-the industrial revolution in the 0/9th century led to the rise of big machines and big cities; In the 20th century, physics was crowned. Physicists split atoms, revealed the wonderful world of relativity and quantum theory, and developed and utilized small silicon wafers. They changed the world through atomic bombs, transistors, lasers and microchips. Now, many experts believe that human beings are ready to meet a new wave of scientific and technological development in the future. As Robert Curl, a chemist at Rice University and winner of the 1996 Nobel Prize, said, "Now is the century of physics and chemistry, but the next century will obviously be the century of biology." Many scientists believe that with the birth of Dolly, a cloned sheep, the century of biology has arrived ahead of schedule.
The breakthrough of cloning technology shocked the world. People worry about human self-replication, but they often ignore the application and significance of other aspects. In fact, it has great theoretical value and broad application prospects in the research and production of basic life science, medicine and family science, and has great potential economic benefits. In the next 5 ~ 20 years, it will gradually form and cause a new world biotechnology industry revolution.
1. In the basic life science, the study of gene function has been carried out in a few animals, such as mice, and now it can be realized in many animals, which is helpful to reveal the gene function and life essence more clearly; It provides one of the most effective means to study the totipotency of mammalian cell development and the relationship between nucleus and cytoplasm. You can also clone various endangered animals, such as giant pandas, golden monkeys and even baiji.
In medicine, it can provide experimental animals with exactly the same nuclear genotype for medical research, which is beneficial for medical scientists to study diseases that have not yet found effective treatments and reveal the pathogenesis; The study of dedifferentiation mechanism is helpful to the study of anti-aging and its mechanism.
3. In agricultural science, excellent animals with strong disease resistance and high production performance can be quickly cultivated and propagated; We can study the pathogenesis of animals and seek new and effective therapeutic drugs.
How can intransitive verbs meet the challenge of "cloning age"
The success of cloning technology marks that the last technical obstacle of "copying" mammals has been broken. In this way, it is theoretically possible to copy humans. Therefore, cloning technology not only brings us benefits, but also brings severe challenges to mankind. Once this technology is applied to human beings, it will bring extremely serious consequences to human society.
1. Humans have returned from sexual reproduction to asexual reproduction.