Reproductive cloning. Shevelukha V. S., Kalashnikova E. A., Degtyarev S. V. Agricultural biotechnology

MOSCOW, October 26 – RIA Novosti. Valery Spiridonov, the first candidate for a body transplant, talks about how modern technologies for cloning living organisms originated and discusses the consequences of their appearance for humanity.

Key of Life

The beginning of research into alternative bioreproduction dates back to 1885, when the German scientist Hans Driesch began studying methods of reproduction, experimenting on sea urchins and other animals with large eggs. In 1902, he managed to raise two full-fledged sea urchins by dividing one embryo into two halves during the first stages of its growth.

A fundamentally new cloning method was developed in the 1940s by Soviet embryologist Georgy Lapshov. He isolated the nucleus of a non-reproductive cell and introduced it into an egg with a previously extracted nucleus. This cloning method is called "nuclear transfer".

American embryologists were later able to conduct similar experiments with frog tadpoles. And in 1996, news about the successful cloning of Dolly the sheep spread throughout the world. It was the first mammal cloned from the cells of an adult.

Subsequently, scientists tried to clone many more animals: mice, pigs, goats, cows, horses, rats and others. In parallel with this, new genetic engineering techniques were created that make it possible to change the DNA of an embryo during cloning and do other fantastic things that are commonplace in science and medicine today.

However, the purpose of such experiments was not only to recreate a population of rare animal species, but also to test cloning technologies and methods to create a copy of a person or his individual tissues.

Copies are illegal. Legislative regulation in Russia and the world

Most countries around the world have temporarily banned cloning. It is primarily due to ethical issues, as well as the imperfections of available technologies. When scientists carry out the cloning process, they simultaneously create hundreds of embryos, most of which do not survive to the implantation stage.

In addition, observations of the length of telomeres, the terminal sections of DNA, show that clones should have a shorter life expectancy than their “parents”, which, however, has not yet manifested itself in observations of actually living clones, despite shorter telomeres than in animals of similar age conceived naturally.

In Russia, since April 19, 2002, the federal law “On a temporary ban on human cloning” has been in force. This document expired in 2007. The moratorium was then extended in 2010 for an indefinite period until a law establishing the procedure for the use of technologies in this area came into force. However, the law does not prohibit the cloning of cells for research purposes or for transplantation.

Despite resistance from politicians and the public, the first laboratory studies and experiments on human embryos have recently been carried out in China, the USA, the UK and the Netherlands. In other countries of the world (for example, in France, Germany and Japan), such experiments still remain outside the law.

If we consider this issue from the point of view of religion, then we can say that any type of cloning is unacceptable for representatives of almost all faiths of the world.

At the moment, there is no reliable information about human cloning experiments conducted. The US National Human Genome Institute, one of the main research centers working in this direction, distinguishes three types of cloning: gene, reproductive and therapeutic.

Gene cloning

Cloning of genes or DNA segments (as defined by the University of Nebraska) is a process in which DNA is extracted from cells, cut into pieces, and then one of those pieces containing a gene is inserted into the genome of another organism. .

As a rule, its role is played by various microbes, whose DNA is much easier to manipulate than the genome of humans or other multicellular living beings, in which the genetic material is packaged inside the nucleus, isolated from the rest of the cell.

Having received several hundred of these microbes with “cloned” foreign DNA, scientists observe how their life activity has changed and select those bacteria that contain interesting genes that can, for example, make plants invulnerable to attacks by various pathogenic fungi or protect them from attacks by pests.

Similarly, “cloning” human genes into microbial DNA allows molecular biologists to search for the causes of various genetic diseases and create gene therapies that can combat them.

Therapeutic cloning

Embryonic stem cells and their analogues, made from “reprogrammed” skin or connective tissue cells, can become virtually any type of cell in the body. This feature allows them to recreate tissues and organs that are compatible with the recipient’s immune system.

In Russia this process is called cell reproduction. It is similar to reproductive cloning, but in this case the growth period of the culture is limited to two weeks. After 14 days, the process of their reproduction is interrupted, and the cells are used in laboratory conditions. For example, to replace damaged tissues. They can also serve to test therapeutic drugs.

Artificial skin is already grown using this method in the UK, and full-fledged bladders are created in the USA.

Reproductive cloning

In the future, cloning could completely solve the problem of infertility - a striking example of this was the famous sheep Dolly.

The source of genetic material was the cells of a deceased sheep, another sheep became the egg donor, and a third animal played the role of a surrogate mother. Of the 277 cells, only 29 developed into an embryo, only one of which survived.

Despite the uniqueness of the experiment and a scientific breakthrough for that time, its results were criticized.

The main reason is that the experiment was not pure from a genetic point of view. In addition to nuclear DNA, part of the genome is contained within the so-called mitochondria, the cellular "power stations". In this case, Dolly inherited mitochondria not from her “genetic” mother, but from an egg donor, which is why she cannot be called a 100% clone. The question arises: is it in principle possible to create an ideal copy of any person or animal?

Are there no absolute clones?

Even if a clone is initially genetically identical to the original, its similarity will inevitably decrease over time. This will be reflected in both external and internal characteristics. Gene therapy using a set of embryonic genes rejuvenated the skin and some organs of elderly mice, paving the way for the creation of rejuvenation techniques for human cells.

In particular, new random mutations constantly arise in the genome of humans and animals, due to which the clone and the original will become different in the first seconds of their “separate” existence. Even natural “clones”, identical twins, initially have several dozen different mutations, and their number gradually increases after their birth.

Moreover, if we remember physics, we will notice that the very laws of quantum mechanics prohibit the existence of ideal copies of any objects.

Uncertain future

However, science does not stand still, and over the past decades, cloning techniques for both genes and organisms have become much safer and more reliable, reducing the likelihood of unsuccessful cloning or errors occurring when transplanting DNA into a foreign organism.

For example, the emergence of cell “reprogramming” techniques allows scientists today to obtain large quantities of stem cells and even grow full-fledged embryos without sacrificing other embryos for this. For now, such cells are used only in laboratories, but in the future they may find their place in the treatment of Parkinson’s diseases, Alzheimer’s diseases, the consequences of strokes, blindness and many other health problems.

The improvement of biotechnology and the accumulation of scientific knowledge in the field of genetic engineering opens up new opportunities for humans: the elimination of genetic diseases, biocompatible transplantology, an alternative solution to infertility problems and, possibly, the birth of children with given parameters.

κλών - “twig, shoot, offspring”) - in the most general sense - exact reproduction of any object. Objects resulting from cloning are called a clone. And both each individually and the entire series.

Human cloning- an action consisting in the formation and cultivation of fundamentally new [ specify] human beings, accurately reproducing not only externally, but also at the genetic level of one or another individual, currently existing or previously existing.

Technology

The technology for human cloning has not yet been developed. Currently, not a single case of human cloning has been reliably recorded. And here a number of both theoretical and technical questions arise. However, today there are methods that allow us to say with a high degree of confidence that the main issue of technology has been resolved.

The most successful method of cloning higher animals was the “nucleus transfer” method. It was he who was used to clone the sheep Dolly in the UK, who lived for six and a half years and left behind 6 lambs, so that we could talk about the success of the experiment. According to scientists, this technique is the best we have today to begin the actual development of human cloning techniques.

The method of parthenogenesis, in which the division and growth of an unfertilized egg is induced, looks more limited and problematic; even if it is implemented, it will only allow us to talk about success in cloning female individuals.

The so-called technology of “splitting” the embryo, although it should produce genetically identical between themselves individuals cannot ensure their identity with a “parent” organism, and therefore cloning technology in the strict sense of the word is not and is not considered as a possible option.

Approaches to human cloning

Human reproductive cloning

Human reproductive cloning - assumes that an individual born as a result of cloning receives a name, civil rights, education, upbringing, in a word - leads the same life as all “ordinary” people. Reproductive cloning faces many ethical, religious, and legal problems that today do not yet have an obvious solution. In some states, reproductive cloning work is prohibited by law.

Therapeutic human cloning

Therapeutic human cloning - assumes that the development of the embryo stops within 14 days, and the embryo itself is used as a product for obtaining stem cells. Legislators in many countries [ specify] they fear that the legalization of therapeutic cloning will lead to its transition to reproductive cloning. However, in some countries (USA, UK) therapeutic cloning is allowed.

Obstacles to cloning

Technological difficulties and limitations

The most fundamental limitation is the impossibility of repetition of consciousness, which means that we cannot talk about the complete identity of individuals, as is shown in some films, but only about conditional identity, the measure and boundaries of which are still subject to research, but identity is taken as a basis for support identical twins. The inability to achieve one hundred percent purity of experience causes some non-identity of clones, for this reason the practical value of cloning is reduced.

Social and ethical aspect

Concerns arise from such points as the high percentage of failures during cloning and the associated possibility of the emergence of defective people. As well as issues of paternity, maternity, inheritance, marriage and many others.

Ethical-religious aspect

From the point of view of the main world religions (Christianity, Islam, Judaism), human cloning is either a problematic act or an act that goes beyond the scope of doctrine and requires theologians to clearly justify one or another position of religious hierarchs.

The key point that causes the greatest rejection is the false premise that in order to obtain a clone of one person, it is supposedly necessary to kill the embryo of another human embryo, which is at a very early stage of development, but has already begun to form (in fact, the classical cloning scheme involves the use of an unfertilized egg, the nucleus of which is replaced the nucleus of a somatic cell - the embryo of another individual does not appear in the scheme; Dolly the sheep and the Kumulina mouse were obtained using this scheme).

As for cloning, as a scientific experiment, it makes sense if it benefits a specific person, but if it is used all the time, there is nothing good in it

At the same time, some non-religious movements (Raelites) actively support developments in human cloning.

Attitude in society

A number of public organizations (WTA) advocate lifting restrictions on therapeutic cloning.

Biological safety

Issues of biological safety of human cloning are discussed. Such as: long-term unpredictability of genetic changes, the danger of leakage of cloning technologies to criminal and/or international terrorist structures.

Human cloning legislation

1996-2001

The only international instrument that prohibits human cloning is the Additional Protocol to the Convention for the Protection of Human Rights and Human Dignity in relation to the Applications of Biology and Medicine, relating to the prohibition of the cloning of human beings, which was signed on January 12, 1998 by 24 countries out of 43 member countries of the Council. Europe (the Convention itself was adopted by the Committee of Ministers of the Council of Europe on April 4, 1997). On March 1, 2001, after ratification by 5 countries, this Protocol entered into force.

2005

On February 19, 2005, the United Nations called on UN member states to pass legislation banning all forms of cloning as they are “contrary to human dignity” and are against the “protection of human life.” The UN Declaration on Human Cloning, adopted by General Assembly resolution 59/280 on 8 March 2005, calls on Member States to prohibit all forms of human cloning to the extent that they are incompatible with human dignity and the protection of human life.

During the discussion at the UN level, several options for a declaration were considered: Belgium, Britain, Japan, South Korea, Russia and a number of other countries proposed leaving the issue of therapeutic cloning to the discretion of the states themselves; Costa Rica, the USA, Spain and a number of others have advocated a complete ban on all forms of cloning.

Criminal liability

Currently, the process of criminalizing human cloning is actively unfolding in the world. In particular, such compounds are included in the new criminal codes of Spain 1995, El Salvador 1997, Colombia 2000, Estonia 2001, Mexico (Federal District) 2002, Moldova 2002, Romania 2004). In Slovenia, a corresponding amendment to the Criminal Code was made in 2002, in Slovakia - in 2003.

In France, amendments to the Criminal Code providing for liability for cloning were made in accordance with the Bioethics Law of August 6, 2004.

In some countries (Brazil, Germany, Great Britain, Japan) criminal liability for cloning is established by special laws. For example, the German Federal Embryo Protection Act of 1990 makes it a crime to create an embryo that is genetically identical to another embryo derived from a living or dead person.

In the UK, the relevant criminal provisions are contained in the Human Reproductive Cloning Act 2001, which provides for a sanction of 10 years' imprisonment. However, therapeutic human cloning is permitted.

In the United States, a ban on cloning was first introduced back in 1980. In 2003, the US House of Representatives passed a law (Human Cloning Prohibition Act of 2003), according to which cloning aimed at both reproduction and medical research and treatment is considered as a felony with a possible 10-year prison sentence and a $1 million fine. In January 2009, the ban on therapeutic cloning was lifted.

In Japan, on November 29, 2000, the Diet passed the “Law Regulating the Use of Human Cloning Technology and Other Similar Technologies,” which contains criminal sanctions.

Human cloning in Russia

Although Russia does not participate in the above-mentioned Convention and Protocol, it has not remained aloof from global trends, having responded to the challenge of the time by adopting the Federal Law “On a temporary ban on human cloning” dated May 20, 2002 No. 54-FZ.

As stated in its preamble, the law introduced a temporary (for a period of five years) ban on human cloning, based on the principles of respect for people, recognition of the value of the individual, the need to protect human rights and freedoms, and taking into account the insufficiently studied biological and social consequences of human cloning. Taking into account the prospects for using existing and developing technologies for cloning organisms, it is possible to extend the ban on human cloning or to lift it as scientific knowledge in this area accumulates and moral, social and ethical standards are determined when using human cloning technologies.

The Act defines human cloning as “the creation of a human being who is genetically identical to another living or deceased human being by transferring the nucleus of a human somatic cell into an enucleated female reproductive cell,” meaning that we are talking only about reproductive cloning, not therapeutic cloning.

According to Art. 4 of the Law, persons guilty of violating it are liable in accordance with the legislation of the Russian Federation.

The law expired in June 2007, and for the next two years the issue of human cloning was not regulated in any way by Russian laws. However, at the end of March 2010, the ban on human cloning in Russia was extended.

The new bill amends the federal law “On a temporary ban on human cloning” to extend the moratorium on cloning for an indefinite period - until the law establishing the procedure for the use of biotechnologies in this area comes into force.

The reason for the ban is stated in the explanatory note to the bill: “Human cloning faces many legal, ethical and religious problems that currently have no obvious solution.”

The new law stipulates that cloning of other organisms, as well as any cells, including human ones, for research purposes is not prohibited.

Some politicians have expressed regret over the extension of the ban on human cloning. In particular, State Duma deputy Vladimir Zhirinovsky said:

We will definitely strive to lift the ban on human cloning - this is necessary for the economy, for demography, for the family, for traditions, this is only beneficial, there is no harm here.

Identity of clones

Contrary to popular misconception, a clone, as a rule, is not a complete copy of the original, since during cloning only the genotype is copied, but the phenotype is not copied.

Moreover, even if they develop under the same conditions, cloned organisms will not be completely identical, since there are random deviations in development. This is proven by the example of natural human clones - monozygotic twins, which usually develop under very similar conditions. Parents and friends can tell them apart by the location of their moles, slight differences in facial features, voice and other characteristics. They do not have identical branching of blood vessels, and their papillary lines are also far from completely identical. Although the concordance of many traits (including those related to intelligence and character traits) in monozygotic twins is usually much higher than in dizygotic twins, it is not always one hundred percent.

Human cloning in popular culture

In science fiction, many authors have written about cloning. Nancy Friedman's novel Joshua, Nobody's Son is about the cloning of an assassinated American president (with the hint that this is John Fitzgerald Kennedy). In Ira Levin's novel "Boys from Brazil" (and in the film based on this novel), Adolf Hitler is cloned, in Anatoly Kudryavitsky's story "Parade of Mirrors and Reflections" - Yuri Andropov. In the children's detective story "The House of the Scorpion", written by Nancy Farmer, tells the story of the life of a clone boy created by a Mexican drug lord. Films from the Star Wars series, Battlestar Galactica, “The Sixth Day”, “The Fifth Element”, “Resident Evil 4: Afterlife”, “Never Let Me Go (film)”, “The Island”, “Another” are devoted to the same topic. "Moon 2112", Brazilian TV series "Clone". The protagonist of the game Hitman is a clone.

Notes

AAAS Policy Brief: Human Cloning USA: “As of 2006, fifteen states had laws dealing with human cloning. All either prohibited reproductive cloning entirely or prohibit the use of government funding for reproductive cloning.", "Many nations, including the UK, China, and South Africa, have explicitly prohibited reproductive cloning while allowing research cloning."
Database on cloning bans in different countries - Global Lawyers and Physicians

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State budgetary educational institution

secondary school No. 571

with in-depth study of English

Nevsky district of St. Petersburg

Abstract on the topic

Cloning

Completed by a student of class 9A

Bobkova Anastasia

Work supervisor - biology teacher

Razuvanova Valentina Vladimirovna

St. Petersburg 2012

Introduction

The last decades of the 20th century were marked by the rapid development of one of the main branches of biological science - molecular genetics. Already in the early 70s, scientists began to obtain and clone recombinant DNA molecules in laboratory conditions and to cultivate plant and animal cells and tissues in test tubes.

A new direction in genetics has emerged - genetic engineering. Based on its methodology, various types of biotechnologies began to be developed and genetically modified organisms (GMOs) were created. The possibility of gene therapy for some human diseases has emerged, and the last decade of the 20th century was marked by another important event - enormous progress has been made in cloning animals from somatic cells.

The developed methods for cloning animals are still far from perfect. During the experiments, high mortality rates of fetuses and newborns are observed. Many theoretical issues of cloning animals from a single somatic cell are still unclear. However, many scientists were enthusiastic about the idea of human cloning. A public opinion poll in the United States showed that 7% of Americans are ready to undergo cloning. At the same time, most scientists and many politicians speak out against the creation of human clones. And their objections and concerns are completely justified.

The purpose of this essay is to identify the positive and negative aspects of cloning.

What is cloning and clone

Initially, the word clone (English cloning from other Greek - “twig, shoot, offspring”) began to be used for a group of plants obtained from one producer plant by a vegetative method. These descendant plants exactly repeated the qualities of their ancestor and served as the basis for developing a new variety. Later, not only the entire group, but also each individual plant in it (except the first) was called a clone, and the production of such descendants was called cloning.

Advances in biology have shown that in both plants and bacteria, the similarity of descendants with the producing organism is determined by the genetic identity of all members of the clone. Then the term cloning began to be used to refer to the production of any lines of organisms that are identical to the given one and are its descendants.

Later, the name cloning was transferred to the technology itself for producing identical organisms, known as nuclear substitution, and then also to all organisms obtained using this technology, from the first tadpoles to Dolly the sheep.

In the late 1990s, there was talk of human cloning. The term ceased to be the property of the scientific community, it was picked up by the media, cinema, literature, computer game producers, and it entered the language as a commonly used word, no longer having the special meaning that it had about a hundred years ago.

Cloning is the exact reproduction of an object any required number of times. Objects obtained as a result of cloning (each individually and their entirety) are called a clone.

Identity of clones

A clone is not a complete copy of the original, since cloning only copies the genotype and does not copy the phenotype. For example, if you take 6 different clones and grow them under different conditions:

· a clone with insufficient nutrition will grow short and skinny;

· a clone that is constantly overfed and limited in physical activity will become obese;

· a clone that was fed a high-calorie diet, poor in vitamins and minerals necessary for growth, will grow short and well-fed;

· a clone that has been provided with normal nutrition and serious physical activity will be tall and muscular;

· a clone that had to carry excessive weights during the growth period will be short and muscular if it is undernourished;

· a clone that was injected with teratogenic substances during embryonic development will have congenital developmental abnormalities.

Even if they develop under the same conditions, cloned organisms will not be completely identical, since there are random deviations in development. For example, monozygotic twins, which usually develop under similar conditions. Parents and friends can tell them apart by the location of their moles, slight differences in facial features, voice and other characteristics. They do not have identical branching of blood vessels, and their capillary lines are also far from completely identical.

History of cloning

Clone - (from the Greek сlon - offspring, branch) is a group of cells or organisms descended from a common ancestor through asexual reproduction and are genetically identical. An example of a clone is a group of bacterial cells formed as a result of the division of the original cell, the descendants of a starfish that regenerated from parts of a divided maternal organism; a clone is also all bushes or trees obtained through vegetative propagation.

However, nature did not “provide” for mammals the ability to reproduce through cloning. A high level of cell differentiation, as if “the other side of the coin,” means that they have lost the ability to give rise to a new organism. However, as practice has shown, the nucleus of even a differentiated cell retains all the potencies necessary to give rise to a new organism.

The essence of cloning is simple: two cells are required - one, which will be the donor of the nucleus and whose owner is cloned, and an egg, the development of which will be controlled by the implanted nucleus. The egg's own nucleus must be destroyed (the cell is enucleated). Experience also shows that for cloning it is better if the egg is not fertilized. The donor cell is forced in one way or another to enter the so-called G0 phase or resting stage. After this, its nucleus is delivered to the egg either by transplantation or cell fusion. The latter is stimulated to divide and begins to form an embryo. The latter is implanted in the uterus of the so-called surrogate mother, where, in case of successful development, it forms a new organism that is genetically identical to the one that was the donor of the nucleus.

Nowadays, two variants of this technique are best known - the so-called Roslyn and Honolulu technologies. The first was used to clone Dolly the sheep by Ian Wilmut and Keith Cambell of the Roslyn Institute in 1996, and the second by a group of scientists from the University of Hawaii in 1998, resulting in fifty mouse clones.

The history of cloning is very rich and dynamic. The first experiments related to cloning, by and large, began to be carried out only about a hundred years ago. Here is a brief list of the main discoveries that made the “copying” of living organisms possible.

1826 - Discovery of the mammalian egg by Russian embryologist Karl Baer.

1883 -- Discovery of the essence of fertilization (fusion of pronuclei) by the German cytologist Oscar Hertwig.

1943 -- Science magazine reported successful in vitro fertilization of an egg.

1962 -- Oxford University zoology professor John Gordon clones clawed frogs (more conclusive experiments - 1970).

1978 -- Louise Brown, the first test-tube baby, is born in England.

1983 -- a mouse was cloned from embryonic cells

1987 -- In the USSR, in the laboratory of Boris Nikolaevich Veprintsev (L. M. Chailakhyan and others), a mouse was cloned from an embryonic cell using the method of electrically stimulated cell fusion.

1985 -- On January 4, in a clinic in north London, a girl was born to Mrs. Cotton - the world's first surrogate mother (conceived not from Mrs. Cotton's egg).

1987 -- Specialists from the George Washington University, using a special enzyme, were able to divide the cells of a human embryo and clone them to the stage of thirty-two cells (blastomeres).

Cloning of animals and bacteria

The possibility of cloning animals was proven by J. Gordon, an English biologist who was the first to obtain cloned clawed frog embryos. He burned the egg nuclei with ultraviolet light and then planted nuclei isolated from the epithelial cells of tadpoles of this species into them. Most of the eggs obtained in this way died, and only a very small proportion (2.5%) developed into tadpoles. It was not possible to obtain adult frogs in this way. Nevertheless, it was a success, and the results of Gordon's experiments found their way into many biology textbooks and manuals. In 1976, Gordon and his co-author R. Lasky published a paper in which they described experiments with nuclei isolated from kidney, skin and lung cells of adult clawed frogs. Researchers first grow these cells outside the body (in vitro) and then inject their nuclei into nuclear-free eggs. A quarter of these eggs begin to divide, but soon freeze at one of the stages of development. Then scientists isolate the nuclei of the resulting embryos and replant them into eggs that have been deprived of their own nuclei... As a result of a whole series of similar transplantations, several tadpoles are finally born. Although the experiments of Gordon and his followers showed the fundamental possibility of obtaining serial clones of amphibians, the emerging tadpoles stubbornly refused to turn into adult frogs. The question, therefore, remained whether it was possible to grow an adult vertebrate animal from one specialized cell of its body. Experiments on amphibians gave negative results, but scientists did not stop research in this area.

Wider research, covering not only amphibians, but also fish, as well as fruit flies, was started in 1962 by the English biologist J. Gordon. In experiments with South African toads Xenopus laevis, he was the first to use not germ cells as a nuclear donor, but already quite specialized cells of the intestinal epithelium of a swimming tadpole.

Then Gordon, together with Lasky (1970), began to cultivate in vitro (outside the body in a nutrient medium) cells of the kidney, lung and skin of adult animals and use these cells as nuclear donors. Approximately 25% of the initially reconstructed eggs developed to the blastula stage. When serially transplanted, they developed to the swimming tadpole stage. Thus, it was shown that the cells of three different tissues of the adult vertebrate (X. laevis) contain nuclei that can support development at least to the tadpole stage.

In turn, Di Berardino and Hofner (1983) used for transplantation the nuclei of non-dividing and fully differentiated blood cells - erythrocytes of the frog Rana pipiens. After serial transplantation of such nuclei, 10% of the reconstructed eggs reached the swimming tadpole stage. These experiments showed that some somatic cell nuclei are capable of maintaining totipotency.

The reasons why the cell nuclei of adult animals and even late embryos remain totipotent have not yet been precisely established. The interaction between the nucleus and the cytoplasm plays a decisive role. Substances contained in the cytoplasm of animals take part in regulating the expression of cellular nuclear genes.

The work of M. di Bernardino and N. Hoffer showed that the cytoplasm of amphibian oocytes contains factors that restore the totipotency of the nuclei of differentiated somatic cells. These factors reactivate repressed regions of the genome.

In 1985, the technology for cloning bony fish developed by Soviet scientists L.A. was described. Sleptsova, N.V. Dabaghyan and K.G. Ghazaryan. Embryos at the blastula stage were separated from the yolk. The nuclei of embryonic cells were injected into the cytoplasm of unfertilized eggs, which began to fragment and develop into larvae. These experiments showed that the loss of totipotency in the nucleus during ontogenesis is not associated with the loss of genes, but with their repression. When culturing somatic cells in vitro, the frequency of nuclear totipotency increases. The genetic mechanism of stable repression of the genome of differentiated cells is not clear, methods for restoring totipotency have not been developed, therefore cloning is mainly carried out by transplanting the nuclei of embryonic cells.

Nuclear transfers in mammals began later, in the 1980s. This was due to technical difficulties, since the mammalian zygote is small. For example, the diameter of a mouse zygote is approximately 60 microns, and the diameter of a fertilized frog egg is about 1200 microns, i.e. 20 times more.

Despite these difficulties, the first reports of obtaining clones of mice identical to the donor appeared already in 1981. Embryonic cells from one of the mouse strains, taken at the blastocyst stage, were used as a donor. The reliability of the data obtained was initially questioned, since it was not possible to reproduce the results of the experiments in other laboratories, but a couple of years later, J. McCrath and D. Salter also achieved success. In these experiments, mouse clones could be obtained only if embryonic nuclei were transplanted at the stage no later than 2 blastomeres. It has been shown that the nuclei of 8-cell embryos and cells of the inner cell mass of the blastocyst do not support the development of in vitro reconstructed eggs even to the morula stage, which precedes the blastocyst stage. A small part (5%) of the nuclei of 4-cell embryos makes it possible to develop only to the morula stage. These and many other data show that during embryogenesis in mice, cell nuclei early lose totipotency, which is obviously associated with the very early activation of the embryo genome - already at the 2-cell stage. In other mammals, in particular in rabbits, sheep and cattle, activation of the first group of genes in embryogenesis occurs later, at the 8-16 cell stage. This may be why the first significant advances in embryo cloning were achieved in mammalian species other than mice. Nevertheless, work with mice, despite their difficult fate, has significantly expanded our understanding of the methodology of cloning mammals.

The first successful experiments in cloning animals were carried out in the mid-1970s by the English embryologist J. Gordon in experiments on amphibians, when replacing the nucleus of an egg with a nucleus from the somatic cell of an adult frog led to the appearance of a tadpole. This showed that the technique of transplanting nuclei from somatic cells of adult organisms into enucleated oocytes makes it possible to obtain genetic copies of the organism that served as a donor of differentiated cell nuclei. The result of the experiment became the basis for the conclusion that embryonic differentiation of the genome is reversible, at least in amphibians.

In their experiment, Campbell and his colleagues extracted a cell from a sheep embryo at an early stage of development (at the embryonic disc stage) and grew a cell culture, that is, they ensured that the cell multiplied in an artificial nutrient medium. The resulting genetically identical cells (cell line) retained totiponency. The scientists then took the egg of the recipient sheep, carefully removed all chromosomal material from it, and ensured that it merged with a totipotent cell from the culture. The resulting synthetic embryos were grown to the morula-blastula stage and then implanted into the uterus of a sheep. As a result, it was possible to raise several normal lambs that were genetically identical.

In principle, once a stable line of totiponent cells has been obtained, nothing prevents genetic changes from being made to them. For example, by rearranging or deleting individual genes, transgenic lines of sheep and other farm animals can be created. However, before this technology finds practical application, many problems still need to be solved.

So far, the number of cloned animals is very small compared to the number of original embryos from whose cells it was possible to obtain a culture. Many cells died before reaching the blastocyst stage. It is not clear whether the high failure rate is due to the variety of harmful factors affecting the cell during manipulation or to the heterogeneity of the cell line itself. The latter is less likely, since the success rate does not change with replanting of the crop. To clarify this issue, it is necessary to study other totipotent cell lines.

The effectiveness of nuclear transplantation into an egg and its subsequent successful development depends on adequate reprogramming of the donor nucleus. Macromolecules (proteins and transfer RNA) of the oocyte are responsible for its development only during a relatively short time (between two cell divisions), and the shorter this period, the less time remains for reprogramming. Cells from more mature embryos take longer to reprogram and are less likely to be successful. The compatibility of the donor nucleus and the recipient cytoplasm, which is still poorly understood, also plays a certain role.

The success of cell nuclear transfer is associated with at least two factors. First, ovulated oocytes are better recipients than zygotes, either because unfertilized eggs have more time to reprogram or because their cytoplasm is more suitable. It is possible that the oocyte cytoplasm contains elements necessary for chromosome rearrangement and genome activation that disappear after fertilization, either because they are somehow associated with replicating DNA or as a result of programmed decay. Secondly, cells with donor nuclei taken at the G1 or G0 stages of the cell cycle develop much better than cells with nuclei from the S or G2 stages. Intuitively, this seems understandable, since it is easier to reprogram an open replicating genome.

Cloning of animals is possible through experimental manipulations with eggs (oocytes) and nuclei of somatic cells of animals in vitro and in vivo, just as identical twins appear in nature. Animal cloning is achieved by transferring the nucleus from a differentiated cell into an unfertilized egg that has had its own nucleus removed (enucleated egg), followed by transplantation of the reconstructed egg into the oviduct of the adoptive mother. However, for a long time, all attempts to apply the method described above to cloning mammals were unsuccessful. A significant contribution to solving this problem was made by a Scottish group of researchers from the Roslyn Institute and PPL Therapeuticus (Scotland) under the leadership of Ian Wilmut. In 1996, their publications appeared on the successful birth of lambs as a result of transplantation of nuclei obtained from fetal sheep fibroblasts into enucleated oocytes. The problem of animal cloning was finally solved by Wilmut's group in 1997, when a sheep named Dolly was born - the first mammal obtained from the nucleus of an adult somatic cell: the oocyte's own nucleus was replaced with a cell nucleus from a culture of mammary epithelial cells from an adult lactating sheep. Subsequently, successful experiments were carried out on cloning various mammals using nuclei taken from adult somatic cells of animals (mouse, goat, pig, cow), as well as taken from dead animals frozen for several years. The advent of animal cloning technology has not only aroused great scientific interest, but also attracted the attention of large businesses in many countries. Similar work is being carried out in Russia, but there is no targeted research program. In general, animal cloning technology is still in its development stage. A large number of organisms obtained in this way exhibit various pathologies leading to intrauterine death or death immediately after birth.

Therapeutic and reproductive human cloning

Human cloning is an action consisting in the formation and cultivation of fundamentally new human beings, accurately reproducing not only externally, but also at the genetic level of a particular individual, currently existing or previously existing.

Therapeutic cloning is used to create a cloned embryo for the sole purpose of creating embryonic stem cells with the same DNA as the donor cell. These stem cells can be used in experiments aimed at studying the disease and inventing new treatments for the disease. To date, there is no evidence that human embryos have been produced for therapeutic cloning.

The richest source of embryonic stem cells is the tissue formed during the first five days after the egg begins to divide. At this stage of development, called the blastoid period, the embryo consists of a group of about 100 cells that can become any type of cell. Stem cells are collected from cloned embryos at this stage of development, ending with the destruction of the embryo while it is still in the test tube. Researchers hope to grow embryonic stem cells, which have the unique ability to transform into virtually any type of cell in the body, in a laboratory that can be used to grow healthy tissue to replace damaged tissue. It is also possible to learn more about the molecular causes of disease by studying embryonic stem cell lines from cloned embryos obtained from animals or humans with various diseases.

Many researchers believe that stem cell research is worthy of the highest attention, since they can help cure a person from many diseases. However, some experts are concerned that stem cells and cancer cells are very similar in structure. And both types of cells have the ability to spread indefinitely, and some studies show that after 60 cycles of cell division, stem cells can accumulate mutations that could lead to cancer. Therefore, the relationship between stem cells and cancer cells must be fully understood before using this treatment technique.

Genetic engineering is a highly regulated technology that is largely studied today and is used in many laboratories around the world. However, both reproductive and therapeutic cloning raise important ethical issues as these cloning technologies can be applied to humans.

Reproductive cloning would present the possibility of creating a person who is genetically identical to another person who once existed or currently exists. This to some extent contradicts long-held religious and social values about human dignity. Many believe that this violates all principles of individual freedom and individuality. However, some argue that reproductive cloning could help childless couples make their dream of becoming parents a reality. Others see human cloning as a way to stop the inheritance of a “harmful” gene. But we must remember that with this type of cloning, stem cells are taken from the embryo located in the experimental tube, in other words, they are killed. And opponents argue that the use of therapeutic cloning is wrong, regardless of whether those cells are used to benefit sick or injured people, because it is wrong to take the life of one to give it to another.

Professor Jonathan Slack at Bass University has succeeded in converting human adult liver cells into insulin-producing pancreatic cells using a simple chemical reaction. Others have restored normal functioning of a spinal cord that had previously been removed. And also, clinical trials using bone marrow to repair heart muscles have been successful, and so on.

Technological difficulties and limitations

Prospects for cloning

1. The use of stem cells to treat diseases characterized by significant tissue damage (stroke, paralysis, diabetes, heart attack, consequences of injuries and burns).

2. Growing organs from stem cells that do not cause rejection.

3. Restoration of extinct species and conservation of rare ones.

Imperial Woodpecker

The last time the imperial woodpecker was seen in Mexico was in 1958. Since then, ornithologists have been trying to find traces of this population, but to no avail. About ten years ago there were even rumors that the bird still lived on the planet, but they were not confirmed.

However, stuffed birds remain in museums. Researcher at the Darwin Museum Igor Fadeev believes that if the DNA extraction operation is carried out with all the stuffed animals that are located in different countries of the world, then the woodpecker can be resurrected. Today, only ten stuffed imperial woodpeckers remain in various museums around the world.

If the project is successful, then in the near future the imperial woodpecker may reappear on our planet. The State Darwin Museum is confident that the latest methods of molecular biology make it possible to isolate and reproduce the DNA of these birds.

Banteng

In 2004, a pair of bantengs (wild bulls native to Southeast Asia) were born, cloned from the cells of animals that had died more than 20 years earlier. The two bantengs were cloned from San Diego's unique "frozen zoo," created before humans even realized cloning was possible. The American company Advanced Cell Technology, which carried out the cloning, said it used cells from animals that died in 1980 without leaving offspring.

Bantengs were cloned by transferring their genetic material into the empty eggs of ordinary domestic cows; out of 16 embryos, only two survived to birth.

Dodo

In June 2006, Dutch scientists discovered on the island of Mauritius the well-preserved remains of the dodo, a flightless bird that became extinct historically recently (in the 17th century). Previously, science did not have the remains of the bird. But now there is some hope for the “resurrection” of this representative of birds.

stem cell cloning human

Cloning of great personalities and the dead

If the tissue sample is frozen properly, a person can be cloned long after their death. In the future, it is possible to create clones from samples of hair, bones, and teeth of famous people of the past.

Attitudes towards cloning in society

It is already known that at least 8 research groups around the world are working on human cloning. Throughout 2002, more and more countries "give legislative approval" to cloning, mainly for therapeutic purposes, despite the active opposition of the Vatican and international acts prohibiting human cloning. Germany, France, Australia and other similarly minded powers are moving in this direction. In the United States, California was the first state to regulate therapeutic cloning.

Using embryos to explore the potential of stem cells could revolutionize medicine, according to experts, by offering the potential for tissue transplants that would prevent or cure many of the most serious human diseases.

An embryo is a spherical collection of cells that develop into a fetus when stem cells begin to differentiate after about 14 days to form the nervous system, spine and other elements of the body. Scientists believe that by isolating stem cells from an embryo when its life span is 3 to 4 days, their growth in the laboratory can be directed in any direction. This will make it possible to grow the desired cells or tissue types for transplants. And one day it will be possible to grow neurons to replace nerve cells in brains dying from Parkinson's disease, to grow skin to treat burns, or pancreatic cells to produce insulin for diabetics.

Theoretically, stem cells can grow into a replacement for almost any part of the human body. If they are obtained from cells taken from the same person for whom the transplant is grown, then there will be no problems with tissue rejection.

Stem cells cells are divided into three main types. The first type, “totipotent” stem cells, are formed during the first divisions of a fertilized egg. They can transform into any type of tissue and form the entire body as a whole. About five days after fertilization, a blastocyst is formed - a hollow vesicle made up of about 100 cells. Those cells that are outside develop into the placenta, and those inside turn into the embryo itself. These 50 or so cells are "pluripotent", they can turn into almost any type of tissue, but not into an entire organism. As the embryo develops further, the stem cells become "multipotent." Now they can only produce specific types of cells. Totipotent and pluripotent cells are also called germline stem cells, and multipotent cells are often called adult stem cells.

What cells are of interest to medicine in terms of cloning? Pluripotent stem cells are of greatest interest to doctors because they can provide all the necessary types of tissue in the human body, but they cannot be turned into a whole human being.

The biggest problem (of a moral and ethical nature, first of all) is that currently the only source of pluripotent cells are human embryos. And this is why anti-abortion groups are so vehemently opposed to stem cell research as well. As for the technical side, there are now three research groups in the world that, through experiments on animals, have developed methods for growing potentially unlimited quantities of multipotent cells in laboratory conditions. But all these methods are primarily focused on embryos.

In general, when a patient receives an organ grown from someone else's cells, there is always the problem of tissue rejection, so the person may need to take immunosuppressant medications for the rest of his life.

However, cloning technology offers a different way. Similar to the method by which the famous cloned sheep Dolly was grown, it is possible to obtain each person's own pluripotent stem cells. To do this, a tissue cell is removed and its nucleus is placed in a donor egg with its own genetic material removed. The egg is then allowed to grow into a blastocyst, from which embryonic stem cells are extracted. This is where the name “therapeutic cloning” comes from.

A group of genes, without which the normal development of embryos is almost impossible, remains unused during the cloning process. It is these genes that may hold the key to improving the procedure for creating genetic copies and treating cancer. There are several key points in the cloning process (from adult cells). Most failures become apparent after a few days, when the blastocyst implants in the uterus. In the experiment that produced Dolly the sheep, only 29 of 277 cloned eggs successfully crossed this barrier.

Rudolf Janisch of the Whitehead Institute found that 70-80 genes that are normally activated in developing mouse embryos are either inactive or have reduced activity in clones. Although it is not clear what these genes do, it is clear that they are turned on at the same time as another gene, Oct4. This gene, in turn, gives embryos the ability to create pluripotent cells - that is, cells that can turn into any tissue. It is possible that some of the genes activated simultaneously are also involved in this process.

Now scientists have to figure out what makes these genes silent. This problem seems fundamental - because if these genes are not turned off in cells in adulthood, this can lead to cancer. It is no coincidence that some of the genes identified by Janisch turn out to be active in tumor cells. It is possible that clones obtained from adult cells suppress what are dangerous genes for adult cells. Even if the mystery of silent genes is solved, cloning a whole animal will still remain a challenge, since the cloned embryo will need to overcome many more problems in later stages of development. It is no coincidence that out of 29 implanted embryos, only one became Dolly the sheep.

From an ethical point of view, opponents of genetic experiments on human cells are convinced that it is immoral to kill the potential for the development of life in a blastocyst. In addition, many are worried that along with honing this whole technique, people will be tempted to clone themselves. But is there another way? Many researchers believe that it may still be possible, in principle, to learn to reverse the evolution of adult stem cells to produce multipotent cells without the need to create a viable embryo. But it is the current raising of the bar for sanctioned research focusing on human cells and embryos that has the potential to accelerate progress in this field.

Conclusion

So, is cloning good or bad? When completing an essay, it is impossible to come to one conclusion. Each person has his own opinion on this matter. But still I will try to summarize the results.

Scientists need science to develop further. They will carry out their experiments even despite the prohibitions.

Doctors are in favor of therapeutic cloning - after all, this will help provide real help to a person and save his life.

Representatives of almost all faiths are against cloning in general, because they claim that man cannot create like God.

Public opinion is also mainly directed against the thoughtless cloning of anything and everything.

Politicians in many countries have issued moratoriums and bills banning cloning activities, at least in humans.

I believe that science, of course, must develop, but bioethical principles must be observed. All achievements of science must be used for the benefit of man.

In some countries, the use of these technologies in relation to humans is officially prohibited - France, Germany, Japan. These prohibitions do not imply that state legislators intend to refrain from using human cloning in the future.

Reproductive cloning. Shevelukha V. S., Kalashnikova E. A., Degtyarev S. V. Agricultural biotechnology

Key of Life

Copies are illegal. Legislative regulation in Russia and the world

Gene cloning

Therapeutic cloning

Reproductive cloning

Are there no absolute clones?

Uncertain future

Technology

Approaches to human cloning

Human reproductive cloning

Therapeutic human cloning

Obstacles to cloning

Technological difficulties and limitations

Social and ethical aspect

Ethical-religious aspect

Attitude in society

Biological safety

Human cloning legislation

1996-2001

2005

Criminal liability

Human cloning in Russia

Identity of clones

Human cloning in popular culture

see also

Notes

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Technological difficulties and limitations

Imperial Woodpecker

The last time the imperial woodpecker was seen in Mexico was in 1958. Since then, ornithologists have been trying to find traces of this population, but to no avail. About ten years ago there were even rumors that the bird still lived on the planet, but they were not confirmed.

If the project is successful, then in the near future the imperial woodpecker may reappear on our planet. The State Darwin Museum is confident that the latest methods of molecular biology make it possible to isolate and reproduce the DNA of these birds.

Banteng

Bantengs were cloned by transferring their genetic material into the empty eggs of ordinary domestic cows; out of 16 embryos, only two survived to birth.

Dodo

stem cell cloning human

Cloning of great personalities and the dead

If the tissue sample is frozen properly, a person can be cloned long after their death. In the future, it is possible to create clones from samples of hair, bones, and teeth of famous people of the past.

Attitudes towards cloning in society

Using embryos to explore the potential of stem cells could revolutionize medicine, according to experts, by offering the potential for tissue transplants that would prevent or cure many of the most serious human diseases.

Theoretically, stem cells can grow into a replacement for almost any part of the human body. If they are obtained from cells taken from the same person for whom the transplant is grown, then there will be no problems with tissue rejection.

What cells are of interest to medicine in terms of cloning? Pluripotent stem cells are of greatest interest to doctors because they can provide all the necessary types of tissue in the human body, but they cannot be turned into a whole human being.

In general, when a patient receives an organ grown from someone else's cells, there is always the problem of tissue rejection, so the person may need to take immunosuppressant medications for the rest of his life.

Literary sources

1. We (novel) (1920) -- E. I. Zamyatin

2. Genome (novel) (1999) -- Sergei Lukyanenko

3. People and casts - Z. Yu. Yuryev

4. Brave New World (1932) -- O. Huxley

5. Lancelot's pilgrimage - Julia Voznesenskaya

6. Shevelukha V. S., Kalashnikova E. A., Degtyarev S. V. Agricultural biotechnology

7. Genetic engineering of plants (laboratory manual) / Ed. J. Raper. - M. Mir, 1991

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