Dolly's cry spread all over the world. The research team led by embryologist ian wilmut of Roslin Institute in Edinburgh cloned this extraordinary lamb from the mammary gland cells of an adult sheep.
First, Wilmatt and his colleagues scraped off several membrane cells from the mammary gland of an unknown white pregnant sheep in FenDorset. Usually, these cells can maintain their activity in 10% fetal serum; Serum is a liquid component of blood, which is rich in cellular nutrients similar to food. Wilmatt realized, however, that by using the standard technique of putting cells in a dormant state, that is, putting them in serum with a concentration reduced to 0.5%, these cells can not only "forget" that they are breast cells, but also "remember" the genetic instructions for developing into a whole sheep.
This is a major breakthrough. Previously, other scientists didn't understand the importance of keeping pace with the development of cellular genetic material. Previously, in other laboratories, genes were too advanced in the development process of egg activation. However, Wilmat cells extracted from Fenndoset ewes did not start to divide DNA and turn it into sheep material. The genes of dormant breast cells can easily combine with egg cells. Then, scientists extracted egg cells from the smaller Scottish black-faced sheep and removed their nuclei (the carrier of DNA) by surgery.
Wilmatt and his research team put the breast cells of white sheep into the egg cells of enucleated black sheep, and used Frankenstein-style technology to not only combine the membranes of these cells with electric pulses, but also instantly merge the two cells into one.
Next, the egg cells thus synthesized are implanted into the black-faced ewe by using standard artificial propagation techniques. Four months later, this little lamb that shocked the world was born. It was found that its coat color was white, suggesting that it did not belong to the same breed as its biological mother, the black-faced ewe. It took several months to examine DNA and finally confirmed that Dolly was indeed a biological replica.
Second, the development of cloning technology.
As early as 1950s, American scientists took amphibians and fish as research objects and pioneered nuclear transplantation technology. They studied the potential of cell development and differentiation and the interaction between cytoplasm and nucleus.
1960 and 1962, scientists from Oxford University in England conducted cloning experiments with an African Xenopus. The experimental method is to irradiate Xenopus laevis eggs with ultraviolet rays to destroy their nuclei, and then take out the nuclei from the intestinal epithelial cells, liver cells and kidney cells of Xenopus laevis tadpoles through superb surgery, and accurately put the nuclei of these cells into the eggs whose nuclei have been destroyed by ultraviolet rays. After careful nursing, some of these nuclear exchange eggs finally grew alive and kicking Xenopus laevis, which was not produced by the combination of sperm cells and egg cells, so it was a cloned Xenopus laevis.
1986, British scientist Wila Anderson cloned a sheep from embryonic cells for the first time through nuclear transfer, and later some people cloned animals such as cattle, sheep, rats, rabbits and monkeys. Recently, the United States successfully cloned monkeys, and Japanese scientists also claimed that they had bred more than 200 "cloned cows". All the cloned animals were successfully transplanted with embryonic cells as donor cells. At present, cloning technology has made new progress in Britain, and they have applied this technology to human hematopoiesis. The economic background of cloning technology Dr. Ross James, director of the British PPL company, said: "From the study of Dolly, we know that we can make an important component from a cell, that is, plasma." They cooperated with Roslin Institute to study a kind of cattle and sheep with human genes. They took plasma from animals first, and then replaced human plasma. This kind of transgenic cattle and sheep contains important components of human plasma. By raising, cloning or breeding these animals, stable, reliable and relatively cheap blood resources can be obtained. According to statistics, the annual value in Britain can reach10.5 million pounds. It can be said that it has benefited a lot.
Author: 2 18.93.58. * Reply to this statement on May 30, 200411.55.
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2 cloning technology
China's cloning technology is not inferior. In 1960s, biologist Tong Dizhou transplanted the nuclei of goldfish and crucian carp, and successfully cloned Rana nigromaculata in 1978. He transplanted the nucleus of the red blood cells of Rana nigromaculata into the pre-peeled eggs of Rana nigromaculata, and finally grew into tadpoles that could swim freely in the water. 1In the spring of 979, scientists from Wuhan Institute of Hydrobiology, Chinese Academy of Sciences artificially cultured the cells in the blastocyst stage of crucian carp. After 59 generations of continuous subculture for 385 days, the nucleus was sucked out of the cultured cells by a glass tube with a diameter of about 65438 00 microns under a microscope. At the same time, the nucleus of crucian carp eggs was removed to prepare the eggs for accepting blastocyst nuclei. After everything is ready, the nucleus sucked out of the glass tube is moved into the empty position of crucian carp eggs, and most of the blastocyst nuclei under artificial culture die prematurely. Of the 189 eggs exchanged by nuclear exchange, only two hatched fry, and finally only one young fish survived the difficulties. After more than 80 days of culture, it grew into a crucian carp with a body length of 8 cm. This kind of crucian carp has not been combined with male and female cells, but only replaced the nucleus of a blastocyst with an egg cell, which is actually produced by the egg after nuclear replacement, so it is also a cloned fish.
With the maturity of fish nuclear exchange technology and the success of amphibian nuclear exchange, a group of scientists engaged in improved seed cultivation are excited. Since the nucleus of crucian carp blastocyst can replace the nucleus of crucian carp egg to obtain cloned fish, can the nuclear exchange of heterogeneous fish obtain new hybrid fish? Scientists in China first put forward this problem and solved it first. They managed to replace the nucleus of carp embryo cells with the nucleus of carp egg cells. The nucleus of carp and the cytoplasm of crucian carp eggs can coexist peacefully and begin a process similar to the division and development of fertilized eggs. Finally, a kind of "crucian carp" with a beard grows very fast, just like carp, but its lateral scales and spines are the same as those of crucian carp, and the taste of fish is no less than that of crucian carp. The emergence of this new species of artificially cloned fish has opened up a new way for fish breeding.
1990 in may, the institute of animal husbandry of northwest agricultural university cloned a goat. 1992, Jiangsu Academy of Agricultural Sciences cloned a rabbit. 1993 The Institute of Developmental Biology of China Academy of Sciences cooperated with the Agricultural College of Yangzhou University to clone a goat. 1In July, 1995, South China Normal University and Guangxi Agricultural University cooperated to clone a hybrid cow of dairy cattle and yellow cattle. 1995 10, Northwest Agricultural University cloned 6 pigs. 199665438+In February, Hunan Medical University cloned 6 mice. In the same year, the Institute of Animal Husbandry of China Academy of Agricultural Sciences cloned a bull. 1In March 1997, Chen Dayuan, a researcher at the Institute of Zoology, Chinese Academy of Sciences, took the lead in proposing the idea of cloning giant pandas. From 65438 to 0999, the team led by Chen Dayuan implanted the somatic cells of giant pandas into enucleated rabbit eggs and successfully cultivated the early embryos of giant pandas. One of the two key problems in cloning giant pandas has been solved.
Thirdly, the influence of cloning technology.
Dolly sheep is the first animal successfully cloned by somatic cells in the world. The success of Dolly's cloning theoretically shows that highly differentiated cells can restore the zygotic function of fertilized eggs after certain treatment. It shows that cytoplasm can regulate the development of heterogeneous nuclei during development. It provides an important way for the treatment of biological genetic diseases, the cultivation of excellent varieties and population expansion, and plays a certain role in the species optimization and population expansion of transgenic animals. In addition, cloning technology can be used to copy a large number of rare animals, save endangered species, adjust the ecological balance of nature and benefit mankind.
Since Dolly the sheep was cloned successfully, countries around the world have aroused strong repercussions, so that both the Vatican and US President Bill Clinton have commented on it. Some people regard it as gospel, while others regard it as disaster. The breakthrough of cloning technology has brought great benefits to mankind. The biggest advantage is that a large number of high-quality livestock have been cultivated, which enriches people's material life, reduces the cost of animal husbandry, improves efficiency, and provides some pharmaceutical raw materials to improve human immune function. Before Dolly's sheep, the Roslin Institute in Britain had bred a transgenic sheep, whose milk contained raw materials for treating hemophilia, and a company bought it at a high price of 500,000 pounds. If we "replicate" this sheep in large quantities with somatic cells, we can save more patients' lives. A ewe was bred by the British company PPL, and its goat milk contained A- 1 antitrypsin, which was used to treat emphysema. The price of this goat's milk is $6,000 a liter. A ewe is like a pharmaceutical factory. What is the most effective and convenient way to breed this kind of sheep? The best way is to "clone". Similarly, the Dutch PHP company has bred cows that can secrete human lactoferrin, and the Israeli LAS company has bred sheep that can produce serum albumin. How can these high value-added livestock breed effectively? The answer is of course "cloning". A mare with a donkey can get an animal with particularly strong heterosis-mule. However, mules cannot reproduce. So, how does an excellent mule expand its reproduction? The best way is also "cloning". The giant panda in China is a national treasure, but its natural mating success rate is low and it is on the verge of extinction. How to save this rare animal "clone" provides a practical way for human beings. In addition, cloning animals plays an important role in studying cancer biology, immunology and human life span.
Undeniably, the appearance of "cloned sheep" has also aroused many people's interest in "human cloning". For example, some people are considering whether they can clone an embryo from their own cells and freeze it before it takes shape. One day in the future, when something goes wrong with one of our own organs, we can take this organ out of the embryo for culture and then replace our diseased organs, which means using cloning technology to provide "accessories" for ourselves. The latest news has seriously disturbed the whole world, especially ethicists. A "cloning" project in the name of "treating diseases and organ transplantation" actually copied human embryos for the first time, which is a blessing or a curse for mankind, which is really unpredictable. Contemporary biological history has proved that cloning technology can only reproduce creatures with the same appearance characteristics, but can't clone the original talents of the copied people. People's thinking ability is conditioned by acquired. Therefore, even if someone can clone people like great leaders and scientists in history, they are just the same in appearance, but they lack the thoughts, temperament and talents of great leaders and scientists. What's the point of such cloning?
The discussion about "human cloning" reminds people that scientific and technological progress is a mixed March. The more science and technology develop, the wider and deeper it penetrates into society, and the more likely it is to cause many related ethical, moral and legal problems. J.D. Watson, a famous molecular biologist who won the Nobel Prize, said, "It can be expected that many biologists, especially those engaged in asexual reproduction, will seriously consider its significance and start scientific discussions to educate people all over the world." At present, American Jielong Company invested $28 million to acquire Roslin Biomedical Company, a subsidiary of Roslin Institute, and obtained the nuclear transplantation technology for cloning Dolly sheep. The main purpose of this transaction is to promote the research of human stem cell cloning technology for organ transplantation. However, this breakthrough research has caused many moral problems. Bioethicists and religious leaders of different sects strongly condemned this, but Washington post said that the US government banned the use of official funds for human embryo research, but private funding was legal. Some ethicists worry that the plan to cultivate human embryonic cells will eventually lead to a large number of human replications.