The problem of cloning

Since1March, 997, the birth of a cloned sheep, named Dolly, has caused a great sensation all over the world. Although this is not the first successful cloning experiment, Dolly shocked the world because she was the first person cloned from mammalian cells, which was previously considered impossible. This means that the possibility of human cloning has increased. For fear of realizing human cloning, many countries have taken necessary measures to regulate the research of human cloning. Some people, such as scientists in this field and some infertile couples, are now opposed to banning it. But I think we should ban human cloning, because it may reduce the value of our lives, take away the personality in our society, and destroy the moral and social system cultivated by human beings for a long time.

Richard Seed, a physicist who supports human cloning, said in a radio interview that he would open a clinic for human cloning for infertile people and make a lot of money (Hotwired Japan). If human cloning is allowed, many people like Seed will make money by cloning technology. Enterprises operating this technology look very profitable, because according to a report, there may be about100,000 women in the United States who want to have similar opportunities to use cloning to have their own children (Watson). Perhaps, they don't care how much it costs to have their own biological baby. Allow h ......

What is cloning technology?

Cloning technology-an epoch-making impact

1On February 22nd, 997, Wilmut, a scientist from Roslin Institute in England, and others announced the success of cloning sheep with somatic cells, which caused great shock in the world. For a time, Dolly the cloned sheep became the most dazzling "star" in the animal kingdom, and its "baa baa" sound quickly spread all over the world.

"Clone" is a transliteration of the English word "clone", which itself means asexual reproduction, that is, a pure cell line formed by the division and reproduction of the same ancestor cells, and each cell in this cell line has the same genes.

Cloning technology is called "biomagnification technology" in modern biology, which has gone through three development periods: the first period is microbial cloning, that is, a bacterium quickly replicates thousands of identical bacteria and becomes a bacterial colony; 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 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.

As early as 1950s, American scientists took amphibians and fish as research objects and pioneered nuclear transplantation technology. 1986, British scientist Wila Anderson cloned a sheep with embryonic cells. Later, some people cloned animals such as cows, mice, rabbits and monkeys. By using embryonic cells as donor cells for nuclear transfer, the birth of these cloned animals was successful.

Dolly the cloned sheep used mammary epithelial cells (somatic cells) as donor cells for nuclear transfer, which turned a new page in the history of biological cloning, broke through the traditional way of nuclear transfer using embryonic cells and made great progress in cloning technology.

Dolly the cloned sheep has no father, only three mothers. The whole cloning process is as follows:

First, scientists took an ordinary cell from the mammary gland of a 6-year-old Dorset ewe A (Dolly's biological mother) from Finland, and isolated the gene of this cell for later use.

Then, scientists take out the unfertilized egg cell of another ewe B (Dolly's borrowed mother), take out the gene in this egg cell, and replace it with the gene of the mammary gland cell of ewe B to form an egg cell containing new residues, and then activate this gene through the discharge of the "switched" egg cell to promote its division and development into an embryo.

Finally, the embryo grew to a certain extent, implanted into the uterus of the third ewe C (Dolly's surrogate mother), and gave birth to Dolly through normal pregnancy.

Dolly completely inherited all the DNA genetic characteristics of Dorset ewe, which is a 100% "copy" of Dorset ewe.

The phenomenon of asexual reproduction exists in lower plants, but according to the law of the mammalian world, animal reproduction should be completed by bisexual germ cells. Because the genetic material of father and mother accounts for half of the offspring, the offspring is definitely not a copy of their parents. The birth of cloned sheep means that human beings can produce the same life in large quantities with one cell of mammals, completely breaking the eternal laws of nature. This is a milestone in the development history of bioengineering technology and a major scientific breakthrough in human history.

Cloning technology is known as "inexhaustible gold mine", which is of great significance in production practice and has great potential economic value. First of all, in the utilization of animal heterosis, compared with conventional methods, mammalian cloning technology takes less time, and the selected breeding stocks are stable; Secondly, cloning technology can play an important role in saving endangered rare species and protecting biodiversity. Even if the success rate of natural mating is low, researchers can choose suitable somatic cells from endangered rare animals for asexual reproduction, thus effectively protecting these species.

The great breakthrough of animal cloning technology has also brought widespread controversy. Cloning technology is a double-edged sword for human beings. On the one hand, it can bring many benefits to human beings ―― such as maintaining excellent varieties, saving endangered animals and using the same genetic background of cloned animals for biomedical research. ......

What is cloning technology?

Cloning technology is asexual reproduction technology. Usually, sexual reproduction includes mating between males and females, combining with eggs to develop embryos and producing new individuals after pregnancy. Cloning technology does not require mating between males and females, and does not require the combination of * * 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.

What is cloning technology?

"clone" is a transliteration of the English word "clone", which has three different meanings in the field of biology.

1. At the molecular level, cloning generally refers to DNA cloning (also called molecular cloning). It refers to inserting specific DNA fragments into vectors (such as plasmids and viruses) by recombinant DNA technology, and then replicating in host cells to obtain a large number of identical DNA fragments "groups".

2. At the cellular level, cloning is essentially a cell group formed by the division of a single ancestor cell. These cells all have the same gene. For example, a cell group with the same genetic background formed by dividing a cell in vitro culture medium for several generations is a cell clone. For another example, in vertebrates, when foreign substances (such as bacteria or viruses) invade, specific recognition antibodies will be produced through immune response. All plasma cells that produce specific antibodies are formed by B cell division, and such plasma cell groups are also cell clones. Cell cloning is a low-level reproductive mode-asexual reproduction, that is, offspring and parents have the same heredity and do not need sexual union. The lower the level of biological evolution, the more likely it is to adopt this mode of reproduction.

3. At the individual level, cloning refers to a group of two or more individuals with the same genotype. For example, two identical twins are a clone! Because they come from the same egg cell, their genetic background is exactly the same. According to this definition, "Dolly" cannot be said to be a clone! Because "Dolly" is just a lonely one. Only by transplanting two or more identical nuclei into two or more identical enucleated eggs and obtaining two or more Dollies with the same genetic background can British embryologists use the word cloning. Therefore, in the sensational paper published in Nature from 65438 to February 1997, the author did not describe Dolly as a clone.

What is cloning?

Cloning is a transliteration of the English word "clone", which is generally translated as transplanting or copying in Taiwan Province Province, Hongkong and Macau. It is a process of using biotechnology to produce offspring that are exactly the same as the original individual genome through asexual reproduction.

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.

The cloned English word "clone" comes from the Greek word "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 the pronunciation of "o" is 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". The Chinese translation of this word is transliterated as "clone" in Chinese mainland, but it is often translated as "copy" in Hong Kong and Taiwan. The former "clone" is like the transliteration "copy" of copy, which has the disadvantage of not looking at the meaning of the text; The latter "copy" can roughly express the meaning of cloning, but it is inaccurate and easy to misunderstand.

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 one individual (for example, by PCR), then inserting it into another individual (usually by vector), and then studying or utilizing it. Cloning sometimes refers to the successful identification of a gene with a certain phenotype. 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 progress

Modern cloning techniques, including nuclear transfer, have been successfully tested in some species (in chronological order):

Frog: 1962, unsuccessful.

Carp: 1963, China scientist Tong Dizhou successfully cloned a female carp by inserting the DNA of a male carp into the egg of a female carp as early as 1963, which was 33 years earlier than Dolly's cloning. 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. (From: Public Broadcasting Company)

Sheep: 1996, Dolly

Macaque: Tetra, female, June 5438 +2000 10.

Pigs: in March 2000, 5 Scottish PPL piglets; August, Xena, female

Cattle: 200 1 year, alpha and beta, male.

Cat: 200 1 ending, plagiarist (CC), female.

Mouse: In 2002

Rabbit: It was independently realized in France and South Korea from March to April, 2003;

Mule: May 2003, Gem, Idaho, male; June, Utah pioneer, male

Deer: Dewey in 2003.

Ma: Prometea, female, 2003.

Dog: 2005, experimental team of Seoul National University, South Korea, Snaby.

Although great progress has been made in cloning research, the success rate of cloning is still quite low: before Dolly was born, researchers experienced 276 failed attempts; After 9000 attempts, 70 calves were born, and one third of them died at an early age. Prometea also made 328 attempts to be born successfully. Right? ......

Advantages and disadvantages of cloning.

We look at human cloning from the perspective of moral values from the following aspects: First, from the perspective of social ethics, human cloning is an overly strong intervention in human development, which may affect the natural structure and development of human beings. Second, from the perspective of family ethics, diversification will aggravate the tendency of family, disintegrate the normal interpersonal order, change the interpersonal relationship department of parents and lose the basic sense of belonging. Thirdly, from the perspective of ethics, it has completely changed the nature of human beings, and the sex-based reproductive mode has separated the generations and genders of the population and destroyed human feelings. Fourthly, from the perspective of bioethics, damaging the rights of people with unique genes may lead to the degradation of human beings and shake the normal view of life and death.

Some scholars also critically reflect on the potential adverse consequences of cloning technology from a broader perspective. Apart from the moral level, this is also reflected in the following aspects: firstly, the gene replication in the ecological dimension and the leading cloning technology will threaten the maintenance of genetic diversity, and biological evolution has undergone a reversal process, that is, from complexity to simplicity, which is extremely unfavorable to the survival of organisms. Secondly, at the cultural level, human reproductive cloning is a substitution, negation and breakthrough to nature. ......