求一段关于克隆过程的英文解释?谢谢!急!

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求一段关于克隆过程的英文解释?谢谢!急!

求一段关于克隆过程的英文解释?谢谢!急!
求一段关于克隆过程的英文解释?谢谢!急!

求一段关于克隆过程的英文解释?谢谢!急!
Cloning in biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments (molecular cloning), cells (cell cloning), or organisms. More generally, the term refers to the production of multiple copies of a product such as digital media or software.
Reproductive cloning
Reproductive cloning uses "somatic cell nuclear transfer" (SCNT) to create animals that are genetically identical. This process entails the transfer of a nucleus from a donor adult cell (somatic cell) to an egg which has no nucleus. If the egg begins to divide normally it is transferred into the uterus of the surrogate mother.
Such clones are not strictly identical since the somatic cells may contain mutations in their nuclear DNA. Additionally, the mitochondria in the cytoplasm also contains DNA and during SCNT this DNA is wholly from the donor egg, thus the mitochondrial genome is not the same as that of the nucleus donor cell from which it was produced. This may have important implications for cross-species nuclear transfer in which nuclear-mitochondrial incompatibilities may lead to death.
Dolly the Sheep
Main article: Dolly the Sheep
Dolly (1996-07-05 – 2003-02-14), a Finn Dorsett ewe, was the first mammal to have been successfully cloned from an adult cell, though the first actual thing to be cloned was a tadpole in 1952[1]. She was cloned at the Roslin Institute in Scotland and lived there until her death when she was six. On 2003-04-09 her stuffed remains were placed at Edinburgh's Royal Museum, part of the National Museums of Scotland.
Dolly was publicly significant because the effort showed that the genetic material from a specific adult cell, programmed to express only a distinct subset of its genes, can be reprogrammed to grow an entire new organism. Before this demonstration, there was no proof for the widely spread hypothesis that differentiated animal cells can give rise to entire new organisms.
Cloning Dolly the sheep had a low success rate per fertilized egg; she was born after 277 eggs were used to create 29 embryos, which only produced three lambs at birth, only one of which lived. Seventy calves have been created from 9,000 attempts and one third of them died young; Prometea took 328 attempts. Notably, although the first clones were frogs, no adult cloned frog has yet been produced from a somatic adult nucleus donor cell.
There were early claims that Dolly the Sheep had pathologies resembling accelerated aging. Scientists speculated that Dolly's death in 2003 was related to the shortening of telomeres, DNA-protein complexes that protect the end of linear chromosomes. However, other researchers, including Ian Wilmut who led the team that successfully cloned Dolly, argue that Dolly's early death due to respiratory infection was unrelated to deficiencies with the cloning process.
Species cloned
Further information: List of animals that have been cloned
The modern cloning techniques involving nuclear transfer have been successfully performed on several species. Landmark experiments[clarification needed] in chronological order:
* Tadpole: (1952) Many scientists questioned whether cloning had actually occurred and unpublished experiments by other labs were not able to reproduce the reported results.[citation needed]
* Carp: (1963) In China, embryologist Tong Dizhou cloned a fish. He published the findings in a Chinese science journal which was never translated into English.[4]
* Mice: (1986) A mouse was the first successfully cloned mammal. Soviet scientists Chaylakhyan, Veprencev, Sviridova, and Nikitin had the mouse "Masha" cloned. Research was published in the magazine "Biofizika" volume ХХХII, issue 5 of 1987.[clarification needed][5]
* Sheep: (1996) From early embryonic cells by Steen Willadsen. Megan and Morag[citation needed] cloned from differentiated embryonic cells in June 1995 and Dolly the sheep from a somatic cell in 1997.[6]
* Rhesus Monkey: Tetra (female, January 2000) from embryo splitting[7][clarification needed]
* Gaur: (2001) was the first endangered species cloned.[8]
* Cattle: Alpha and Beta (males, 2001) and (2005) Brazil[9]
* Cat: CopyCat "CC" (female, late 2001), Little Nicky, 2004, was the first cat cloned for commercial reasons[citation needed]
* Mule: Idaho Gem, a john mule born 4 May 2003, was the first horse-family clone.[citation needed]
* Horse: Prometea, a Haflinger female born 28 May 2003, was the first horse clone.[citation needed]
* Water Buffalo: Samrupa was the first cloned water buffalo. It was born on February 6, 2009, at India's Karnal National Diary Research Institute but died five days later due to lung infection.[10]
Human cloning
Main article: Human cloning
Human cloning is the creation of a genetically identical copy of an existing or previously existing human. The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace, with their cloning occurring during the natural process of reproduction. There are two commonly discussed types of human cloning: therapeutic cloning and reproductive cloning. Therapeutic cloning involves cloning cells from an adult for use in medicine and is an active area of research: while reproductive cloning would involve making cloned human beings. Such reproductive cloning has not been performed and is illegal in many countries. A third type of cloning called replacement cloning is a theoretical possibility, and would be a combination of therapeutic and reproductive cloning. Replacement cloning would entail the replacement of an extensively damaged, failed, or failing body through cloning followed by whole or partial brain transplant.
The various forms of human cloning are controversial.[11] There have been numerous demands for all progress in the human cloning field to be halted. Some people and groups oppose therapeutic cloning, but most scientific, governmental and religious organizations oppose reproductive cloning. The American Association for the Advancement of Science (AAAS) and other scientific organizations have made public statements suggesting that human reproductive cloning be banned until safety issues are resolved [12]. Serious ethical concerns have been raised by the idea that it might be possible in the future to harvest organs from clones. Some people have considered the idea of growing organs separately from a human organism - in doing this, a new organ supply could be established without the moral implications of harvesting them from humans. Research is also being done on the idea of growing organs that are biologically acceptable to the human body inside of other organisms, such as pigs or cows, then transplanting them to humans, a form of xenotransplantation.
The first human hybrid human clone was created in November 1998, by American Cell Technologies.[13]. It was created from a man's leg cell, and a cow's egg whose DNA was removed. It was destroyed after 12 days. Since a normal embryo implants at 14 days, Dr Robert Lanza, ACT's director of tissue engineering, told the Daily Mail newspaper that the embryo could not be seen as a person before 14 days. While making an embryo, which may have resulted in complete human had it been allowed to come to term, according to ACT: "[ACT's] aim was 'therapeutic cloning' not 'reproductive cloning'"
On January, 2008, Wood and Andrew French, Stemagen's chief scientific officer in California, announced that they successfully created the first 5 mature human embryos using DNA from adult skin cells, aiming to provide a source of viable embryonic stem cells. Dr. Samuel Wood and a colleague donated skin cells, and DNA from those cells was transferred to human eggs. It is not clear if the embryos produced would have been capable of further development, but Dr. Wood stated that if that were possible, using the technology for reproductive cloning would be both unethical and illegal. The 5 cloned embryos, created in Stemagen Corporation lab, in La Jolla, were destroyed.[14]
Ethical issues of cloning
Main article: Ethics of cloning
Although the practice of cloning organisms has been widespread for several thousands of years in the form of horticultural cloning, the recent technological advancements that have allowed for cloning of animals (and potentially humans) have been highly controversial. Some believe it is unethical to use a human clone to save the life of another. Others have countered that people who exist today and have interpersonal relationships and personal histories should take precedence over never-conscious life at any stage of developmental maturity. The Catholic Church and many religious organizations oppose all forms of cloning, on the grounds that life begins at conception. Conversely, Judaism does not equate life with conception and, though some question the wisdom of cloning, Orthodox rabbis generally find no firm reason in Jewish law and ethics to object to cloning.[15] From the standpoint of classical liberalism, concerns also exist regarding the protection of the identity of the individual and the right to protect one's genetic identity.
Gregory Stock is a scientist and outspoken critic against restrictions on cloning research.[16]
The social implications of an artificial human production scheme were famously explored in Aldous Huxley's novel Brave New World.
According to the US Food and Drug Administration, food coming from cloned animals is safe to eat. In addition the FDA stated that cloned food does not require special labeling. Both meat and milk from cloned animals such as swine, goats and cattle have no differences from the conventionally bred animals.
Joseph Mendelson, legal director of the Center for Food Safety, said that cloned food still should be labeled due to the fact that safety and ethical issues of it remain questionable.
Carol Tucker Foreman, director of food policy at the Consumer Federation of America, stated that FDA does not consider the fact that the results of some studies revealed that cloned animals have increased rates of mortality and deformity at birth.
FDA specialists mentioned that when the cloned animals are aged from 6 to 18 months, they are almost similar to conventionally bred animals. The food receives a certain label only in cases when its features are modified by the way it is produced. [17]