The recent report by Chinese scientists about the birth of cloned monkeys did not surprise specialists, but caused concern in the community. After all, this means that science has come close to the genetic copying of humans. RIA Novosti publishes a selection of the most famous clones of mammals that have successfully grown and even given offspring.
Mammals reproduce their own kind using a rather cunning mechanism: conception takes place inside the body, and an embryo develops there, from which a baby, ready for life outside the mother's womb, grows in weeks or months. It carries the genes of the father and mother, so it never turns out to be an exact genetic copy of one of them, that is, a clone.
Genetic copies of an organism are created naturally when one egg divides in half or several times. As a result, identical twins are born - with the same genomes. To create a copy of another organism without an egg, artificial intervention is required. DNA from an adult cell that needs to be cloned is placed in a foreign egg, previously purified from its own DNA. An egg cell with foreign DNA is introduced into the oviduct of a female ready to bear and wait for the allotted time until the baby is born. Thus, there are three different organisms involved in cloning: a DNA donor, an egg donor, and a surrogate mother.
The first cloning experiments were carried out in the 1950s on frogs. It was possible to grow an adult from a clone in 1962 in Oxford (Great Britain). For these studies, biologist John Gurdon was awarded the Nobel Prize.
Cloning is a very risky process, since not every egg starts dividing and not every embryo placed in a surrogate mother survives. This imposes restrictions on experiments with mammals, whose organism also takes a long time to develop. So far, cloning mammals is laborious and expensive.
As for humans: in 2013, in the United States, scientists led by Shukhrat Mitalipov managed to transplant the nucleus of a skin cell into a donor egg and force it to divide. The embryo developed successfully for several days, after which the experiment was interrupted to extract the stem cells. Since the matter did not reach the surrogate mother, strictly speaking, this experience cannot be called cloning.
Mouse
Promotional video:
For the first time, a mammal was cloned by Soviet scientists under the leadership of Levon Chailakhyan from the Institute of Biological Physics of the Academy of Sciences of the USSR, as reported by the journal "Biophysics" in 1987. Using electrical stimulation, biologists fused an embryonic cell with an egg cell of an albino house mouse purified from genetic material. As a result, three clone mice were born.
Sheep
Animal cloning experiments have long attracted the attention of only a narrow circle of molecular biologists. The public and politicians became interested in this in 1997, when the British scientist Ian Wilmut made public the details of an experiment with sheep cloning. The clone was named Dolly. It was the only surviving individual of 277 artificial embryos. Dolly left offspring, but lived only six years. She had to be put to sleep due to arthritis and lung disease. Scientists suggest that Dolly has aged ahead of time.
Dolly the cloned sheep / AFP 2018 / Colin McPherson.
Cat
The first clone of a cat was born after 87 unsuccessful attempts in December 2001 at Texas A&M University (USA). The female was named Sisi after the initial letters of the phrase Copy Cat. DNA for her was taken from a tricolor cat, and Sisi was born white and brown. Scientists explained this by the fact that color is determined more by factors of fetal development than by genes. This experience also showed that a genetic copy can be outwardly different from its sample.
When Sisi grew up, she was taken home by one of the laboratory staff. The cat gave birth to completely healthy kittens three times. She recently turned 15, and this is another reason for surprise, since the main argument against cloning is that sick individuals develop from cloned embryos.
Duane and Shirley Cramer with CC (left) and three kittens in 2006 / Photo: Texas A & M University.
Horse
In May 2003, a clone of a mule named Idaho Jem was born at the University of Idaho (USA). He was carried away by a mare, and a mule, a champion in racing, became the donor of genetic material. The clone was also expected to win. Actually, the sponsor who funded the study was breeding horses.
Three years later, Idaho Jem competed with naturally born mules. Finished third. It was reported that the mule ended his sports career and is being kept in a private household.
At the same time, the first cloned horse named Prometheus was born in the laboratory of reproductive technologies in Italy. Scientists made 327 attempts before they managed to grow a clone.
The world's first horse clone / AFP 2018 / Vincenzo Pinto.
Dog
The first dog clone was born on April 24, 2005 at Seoul National University in South Korea. It was an Afghan Hound puppy obtained from the ear skin DNA of a three-year-old male. Snappy, as the clone was named, is the only surviving of 1,095 embryos that were planted in 123 surrogate bitches.
Since the project was led by biologist Hwang Woo-seok, who was previously convicted of a forgery with human stem cells, the scientific community doubted Snappy as well. However, an independent scientific laboratory hired by the university to verify the results of the experiment confirmed that the puppy is indeed a clone.
Camel
In Dubai (UAE), at the Camel Reproduction Center, on April 8, 2009, a 30-kilogram camel Injaz (in Arabic - "achievement") was born. She is a genetic copy of a camel that died in 2005. Injaz grew up healthy, fertile and in 2015 gave birth to a daughter.
In the UAE, camel cloning is in demand in the sports industry / Depositphotos / Zambezi.
A monkey
In January 2018, Chinese scientists at the Center for Primate Research at the Institute of Neurophysiology in Shanghai announced the birth of two clones of the Javanese macaque. The Chinese followed the Dolly sheep method and modernized it. Females Zhong Zhong and Hua Hua were placed in an incubator. The primates are perfectly healthy.
Commenting on the results of the experiment, one of its participants, biologist Mu-Ming Poo, said in an interview with Nature: "There are technically no obstacles to cloning a person."
Monkeys Zhong Zhong and Hua Hua / AP Photo / Jin Liwang / Xinhua.
Olga Kolentsova, Tatiana Pichugina