Cloning: the main events from the XIX century to the present day
History of cloning experiments
The term "cloning" describes a number of different processes, as a result of which a genetic copy of a biological organism can be created. The "copied" material, which has a genetic composition similar to the "original", is called a "clone".
In the 1880s, August Weismann, professor of zoology and comparative anatomy at the University of Freiburg, suggested that genetic information is gradually reduced with each cell division.
Weissmann's theory was experimentally confirmed by the German embryologist Wilhelm Roux. When he used a hot needle to destroy one of the cells of a two-celled frog embryo, only half of the embryo developed.
In 1894, German biologist Hans Driesch challenged the theory of Weissmann and Roux, experimentally revealing that blastomeres (cells formed as a result of zygote fragmentation) isolated from two- and four-cell sea urchin embryos are capable of developing into small larvae.
In 1901, the German scientist Hans Spemann divided the two-celled embryo of a salamander into two parts, each of which developed into a full-fledged organism. The result of the experiment confirmed that at an early stage of development, embryonic cells contain sufficient information to create an independent organism.
In 1902, the American geneticist Walter Sutton hypothesized that the genetic information of the chromosome is contained in the cell nucleus.
In 1914, Hans Spemann conducted the first experiments on the transplantation of a nucleus from one cell to another.
In 1938, Spemann suggested that it was possible to transplant the nucleus of a single cell into a nuclear-free egg.
Thus, the theoretical basis for subsequent cloning experiments was laid.
In 1962, John Gurdon, a professor at Oxford University, claimed to have cloned a South African frog. He managed to achieve the development of frog eggs with a foreign nucleus until quite late stages, in about two percent of cases, individuals turned into adult frogs. In 2012, Gurdon was awarded the Nobel Prize in Medicine or Physiology for his research.
In 1963, British biologist John Haldane first used the term "clone".
In the same year, Chinese researcher Tong Dizhou cloned fish for the first time. He transplanted the genetic material of an adult Asian carp into an egg, from which a new individual emerged, which subsequently brought offspring.
In 1964, Cornell University professor Frederic Steward grew a whole carrot from completely isolated rhizome cells, thus proving the possibility of cloning using differentiated (isolated) cells.
In 1979, Karl Illmensee claimed that he had managed to clone three mice.
In 1983, Kary Mullis developed a polymerase chain reaction (PCR) method that allows for a significant increase in small concentrations of certain nucleic acid fragments (DNA) in biological material (sample).
In 1984, the Danish scientist Steen Willadsen cloned a sheep from embryonic cells. This was the first experiment in cloning a mammal. Willadsen used the nuclear transfer method.
In 1986, Willadsen cloned a cow from differentiated cells of a one-week-old embryo.
In the same year, University of Wisconsin professors Neal First, Randal Prather and Willard Eyestone also cloned a cow from embryo cells.
In 1995, Ian Wilmut and Keith Campbell, professors of the Roslin Institute in Scotland, successfully cloned two sheep, Megan and Morag, using the genetic material of two isolated embryos.
In 1996, Wilmut and Campbell first conducted an experiment on cloning an animal from adult cells, as a result of which Dolly the sheep was born on July 5, 1996.
On February 27, 1997, the English journal Nature published a sensational article by embryologist and geneticist Ian Wilmat about the successful cloning of Dolly the sheep.
In 1997, in the laboratory of Don Wolf of the Oregon Regional Primate Research Center, scientists managed to clone two rhesus monkeys.
In the same year, US President Bill Clinton banned the use of public funds to finance human cloning. (In fact, such work has never been carried out, and it was forbidden to allocate state funds to obtain new lines of human embryonic stem cells. At the state expense, it was allowed to continue experiments with only a small number of CESC–VM lines available at that time.)
In 1997, Ian Wilmut and Keith Campbell used laboratory–grown skin cells with a human gene genetically implanted in them and cloned another sheep, Polly.
In 1998, Dolly gave birth to three healthy lambs conceived naturally.
In the same year, at the University of Hawaii, a group of scientists led by Professor Ryuzo Yanagimachi cloned 50 mice from adult cells. The first clone mouse was nicknamed Kumulin.
On March 5, 2000, British scientists conducted the first successful pig cloning operation.
On December 22, 2001, the world's first cloned domestic cat named Cece (CopyCat, CC) was born at Texas A&M University (Texas A&M University). Two years later, the first cloned deer, Dewey, and the first cloned horse, Prometheus, were born at the university.
In 2001, scientists from Advanced Cell Technology, Inc. announced the birth of a gaura bull named Noah, which became the first cloned animal belonging to an endangered species. This experiment opened up the prospect of saving endangered animal species by cloning.
In 2003, the world-famous Dolly sheep was euthanized. The cause was progressive lung cancer caused by a virus. Dolly was 6.5 years old.
In 2005, the world's first cloned dog, the African greyhound Snappy, was born in South Korea.
In 2009, the first cloned camel, Injas, was born in Dubai (UAE), translated from Arabic as "achievement".
In June 2013, a group of scientists from the Japanese RIKEN research center managed to clone a mouse using leukocytes isolated from a drop of peripheral blood of an animal. Previously, leukocytes were not used for cloning.
Despite a number of statements about successful experiments on cloning a human embryo (1998, 2004 – in South Korea, 2002 – in the USA), there was no scientific confirmation of this.
In 2013, in the USA, a native of Kazakhstan, Shukrat Mitalipov, was able to extract stem cells from embryos grown from human skin cells. A research team led by Professor Mitalipov of the Oregon Health and Science University extracted DNA from a donor egg obtained from a young woman, placed genetic information from a skin cell in it and forced the cell to divide, but not by stimulating electrical discharges, as in the case of Dolly sheep cells, but by using caffeine. The resulting embryo developed for 5-6 days and reached a size of 120 cells, after which Mitalipov managed to extract living stem cells from it.
According to the British scientist Ian Wilmut, the creator of Dolly the sheep, the existing cloning procedures are very inefficient.
Dolly the sheep was the only survivor of 277 embryos. Subsequent studies have shown that, at best, only 5% of attempts end in success.
The ban on conducting experiments on human reproductive cloning is in effect in Australia, Austria, Argentina, Belgium, Brazil, Canada, the Czech Republic, Denmark, Finland, France, Germany, Italy, Japan, Sweden, Switzerland and other countries.
In 2002, Russia introduced a five-year moratorium on human cloning, which expired in 2007.
In 2010, the State Duma of the Russian Federation adopted a law on the extension of the moratorium. At the same time, the law does not prohibit the cloning of cells and organisms for research purposes, the cultivation of organs for transplantation and the cloning of animals.
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