Cloned English' clone' comes from the Greek' KL! N' (twig) In horticulture, the word "clone" was used until the 20th century. Later, sometimes' e' is added to the end of the word to become' clone' to indicate that' o' is pronounced as a long vowel. Recently, with the widespread use of this concept and word in public life, spelling has been limited to the use of "cloning". In Chinese mainland, the Chinese translation of this word is "clone", while in Hong Kong and Taiwan, it is usually translated as "clone" or "copy". The former "clone" is like the transliteration "copy" of copy, which has the disadvantage of not looking at the literal meaning; The latter's "copy" can roughly express the meaning of cloning, but it is not accurate and easy to be misunderstood.
Cloning is usually artificially induced asexual reproduction or natural asexual reproduction (such as plants). Cloning is a multicellular organism, genetically identical to another organism. Clones can be natural clones, such as asexual reproduction or individuals with identical genes (just like identical twins). But what we usually mean by cloning is an identical copy produced by conscious design.
Cloning technology is called "biomagnification technology" in modern biology, and it has gone through three development periods: the first period is microbial cloning, that is, a bacterium quickly replicates thousands of identical bacteria and becomes bacterial colonies; The second period is biotechnology cloning, such as using genetic gene-DNA cloning; The third period is animal cloning, that is, cloning a cell into an animal. Dolly the cloned sheep was cloned from the somatic cells of ewe by animal cloning technology.
In biology, cloning is usually used in two aspects: cloning a gene or cloning a species. Cloning a gene refers to obtaining a gene from an individual (for example, by PCR) and then inserting it. In addition, there are also asexual reproduction in the animal kingdom, but it is more common in invertebrates, such as the division and reproduction of protozoa, the budding and reproduction of caudate animals and so on. But for advanced animals, under natural conditions, they can only reproduce sexually, so scientists must go through a series of complicated operating procedures to make them reproduce asexually. In 1950s, scientists successfully cloned an amphibian, Xenopus laevis, which opened a new chapter in cell biology.
In the late 1980s, Britain and China successively used embryonic cells as donors to "clone" mammals. By the mid-1990s, China had cloned five kinds of mammals, including mice, rabbits, goats, cows and pigs.
19 dragon produced Dolly the lamb with the same genetic structure as the donor, and the world public opinion was in an uproar. Dolly is special in that its life was born without the participation of sperm. The researchers first sucked genetic material from a sheep's egg cell and turned it into an empty shell, then took out breast cells from a 6-year-old ewe and injected genetic material into the empty shell of the egg cell. In this way, an egg cell containing new genetic material but not refined was obtained. This modified egg cell divides and proliferates to form an embryo, which is then implanted into the uterus of another ewe. With the smooth delivery of ewes, "Dolly" came into this world.
But why don't other cloned animals have such great influence in the world? This is because the genetic genes of other cloned animals come from embryos, and they are all nuclear transplants with embryonic cells, which cannot be strictly said to be "asexual reproduction". Another reason is that the embryonic cell itself is sexually propagated, and the genome in its nucleus is half from the father and half from the mother. Dolly's genome is all from a single parent, which is really asexual reproduction. Therefore, strictly speaking, "Dolly" is the first truly cloned mammal in the world. 1On February 23rd, 997, scientists from Roslin Institute in Scotland, England, announced that the successful use of goat somatic cell "cloning" technology by their research team was the result of scientific development, and it had a very broad application prospect. In horticulture and animal husbandry, cloning technology is an ideal means to cultivate varieties with stable genetic traits. Through cloning technology, high-quality fruit trees and improved livestock can be cultivated. In the medical field, the United States, Switzerland and other countries have been able to use "cloning" technology to cultivate human skin for skin grafting. This new achievement avoids the possible rejection of allogeneic transplantation and brings good news to patients. According to China Xinhua News Agency1April 4, 1997, Cao Yilin, an expert in plastic surgery in Shanghai Ninth Staff Hospital, successfully cloned human ears in mice for the first time in the world, bringing hope for the repair and reconstruction of missing organs. Cloning technology can also be used to breed many valuable genes, such as insulin for treating diabetes, growth hormone that is expected to make dwarfism patients grow taller again, and interferon that can resist many diseases and infections.
Cloning is a major technological breakthrough in the field of biological sciences, which reflects the progress of nuclear differentiation technology, cell culture and control technology. Originally, it was a transliteration of English clone, which means the offspring individual population with the same genotype formed by biological cell asexual reproduction, referred to as "asexual reproduction". The great breakthrough of animal cloning technology has also brought widespread controversy.
The word "cloning" was introduced into horticulture in 1903, and gradually applied to botany, zoology and medicine. Broadly speaking, "cloning" is actually something we often encounter in our daily life, but it is not called "cloning". In nature, many plants have innate cloning instinct, such as sweet potatoes, potatoes, roses and other cutting propagation plants. However, animal cloning technology has experienced the development process from embryonic cells to somatic cells.
In spring, the 6-year-old ewe has exactly the same gene, which can be described as a copy of her mother. It is worth noting that cloning technology will not only bring great benefits to mankind, but also bring disasters and problems to mankind. However, we can't stop its development, because it may bring serious consequences. In the final analysis, its advantages outweigh its disadvantages, and it will be beneficial to the wide application of human beings. Individuals (usually through carriers) then study or use it. Cloning sometimes refers to successfully identifying a certain -{A|zh-cn: phenotype; Zh-tw: dominant gene. So when a biologist says that the gene of a disease has been cloned successfully, that is to say, the position and DNA sequence of this gene have been determined. Obtaining a copy of this gene can be considered as a by-product of identifying this gene.
Cloning an organism means creating a new object with exactly the same genetic information as the original organism. Under the background of modern biology, this usually includes somatic cell nuclear transfer. In somatic cell nuclear transfer, the nucleus of oocytes is removed and replaced by the nucleus taken from cloned organisms. Usually, oocytes and their transplanted nuclei should come from the same species. Because the nucleus contains almost all the genetic information of life, the host oocyte will develop into an organism genetically the same as the nuclear donor. Although mitochondrial DNA has not been transplanted here, it is still relatively rare, and its impact on organisms can usually be ignored.
In horticulture, cloning refers to the offspring of a single plant produced by vegetative propagation. Many plants obtain a large number of offspring from one plant by cloning this asexual reproduction.
Cloning technology can play a role in saving rare and endangered animals, expanding and improving animal populations, providing enough experimental animals, promoting the research of transgenic animals, overcoming hereditary diseases, developing high-level new drugs and producing internal organs for human transplantation, but if it is applied to human reproduction, it will produce a huge ethical crisis.
What did China clone?
Frog: 1952, unsuccessful.
Carp: 1963, as early as 1963, China scientist Tong Dizhou successfully cloned a female carp by injecting the genetic material of a male carp into the egg of a female carp, 33 years earlier than the cloned sheep. However, because the related papers were published in a China sci-tech journal and were not translated into English, they are not well-known internationally.