clone

Cloning is a transliteration of the English word "clone" or "clone", and the English word "clone" comes from the Greek word "Klone", which originally meant to cultivate plants through asexual reproduction or asexual reproduction, such as cutting and grafting. In Chinese mainland, it is translated as "asexual reproduction", and in Taiwan, Hong Kong and Macao, it is generally translated as reproduction or colonization. There are more exact words in Chinese to express cloning, such as "asexual reproduction", "clone" and "pure line". Cloning refers to the asexual reproduction of organisms through somatic cells and the group of offspring individuals with the same genotype formed through asexual reproduction. It is usually a process of organizing offspring by producing exactly the same genes as the original individuals.

Scientists call the process of artificial gene manipulating animal reproduction cloning. This biotechnology is called cloning, which itself means asexual reproduction, that is, a pure cell line formed by the division and reproduction of the same ancestor cell. Every cell in this cell line has the same gene.

Cloning can also be understood as producing the same copy from the prototype, which looks exactly like the prototype. Today, the meaning of "cloning" is not only "asexual reproduction", but also refers to a group of individuals from the same ancestor who reproduce asexually. This group of asexual offspring from the same ancestor is also called "cloning". Simply put, it is 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. By layering, cutting or grafting the roots, stems and leaves of plants to produce new individuals, it is also called asexual reproduction. Animals such as monkeys and cows cannot reproduce asexually without manual operation. Dolly the cloned sheep is also the product of cloning. About the idea of cloning, Wu Cheng'en, a great writer in Ming Dynasty, once described it brilliantly-the Monkey King often pulled out a handful of monkey hair at a critical moment and turned it into a large group of monkeys. This is a myth, of course, but in today's scientific terms, the Monkey King can clone himself very quickly. Theoretically, protein contained in monkey hair is a partial expression of DNA that guides the synthesis of this part of hair (related to its intron and exon), which can be reverse transcribed, that is, cloned, but in fact, our technology has not advanced to such an extent.

Another cloning method is to extract gene cells from two or more people and combine them to form embryos. After the clone is born, it will have the characteristics of several people who provide genes.

Because cloning technology is asexual reproduction, it is not a technology invented according to the principles of gene recombination, gene mutation and chromosome variation.

Basic process

Firstly, the nucleus of a donor cell containing genetic material is transplanted into an egg cell without nucleus, and then the two cells are fused into one by micro-current stimulation, and then the new cell is promoted to divide and reproduce and develop into an embryo. When the embryo develops to a certain extent, it is implanted into the uterus of an animal to make the animal pregnant, so that 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.

Important achievements in recent 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. 1997 In March, nearly 1 month after Dolly was born, scientists from the United States, China, Taiwan Province Province and Australia announced that they had successfully cloned monkeys, pigs and cows. But they are all cloned with embryonic cells, and their significance cannot be compared with that of 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 group is completely different from Dolly's cloning technology, which shows that Chinese scientists have 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.