What has changed in the world of cloning since the days of Dolly the sheep

What is cloning?

CloningCloning Is the creation of genetically identical copies of living organisms or their fragments. You can clone different biological material: individual cells, tissues, organs and whole organisms.

What are the types of cloning?

Molecular cloning

Using this method, scientists isolateGene cloning genes of interest, insert them into a plasmid - a bacterial DNA molecule, and then create a population of such bacteria. Depending on the purpose of the experiment, you can stop there or insert the resulting plasmids into plant and animal cells.

This is how genetically modified organisms: plants resistant to pests, animals with immunity to diseases. Also, with the help of technology, diseases are studied and drugs are developed.

Therapeutic cloning

Scientists grow a clone embryo in a test tube, but do not allow it to develop into a full-fledged organism. For this, a somatic cell is taken from an animal or a person - any cell of the body that does not take part in sexual reproduction, and a nucleus is taken out of it. They also take an egg from another individual of the same species and remove the nucleus.

Then the nucleus is inserted into a non-nuclear egg and the process of division is started. When the cell turns into a blastocyte - a vesicle with embryonic stem cells inside, development is stopped.

Stem cells (progenitor cells) that have not yet decided which cells to turn into can become anything. They are usedTissue engineering, stem cells, cloning, and parthenogenesis: new paradigms for therapy for experiments, for example, scientists are investigating mutations in genes or trying to grow organs and tissues that can be implanted to replace damaged ones.

Reproductive cloning

This view allowsCloning create a genetically identical copy of a whole animal. The mechanism is the same as in therapeutic cloning, only the development of the embryo is not interrupted at the blastocyte stage. Instead, they put him in uterus individuals of the same species where the embryo develops into a full-fledged organism.

What animals have already been cloned?

Dolly is the most famous clone, but far from the first. The history of cloning began a century before the birth of the sheep.

In 1885, Hans Driesch split a two-celled sea urchin embryo and produced two identical twins. Then, in 1902, Hans Spemann used a hair to split the salamander embryo and also got two clones.

Experiments with the transfer of the nucleus into the egg began 50 years later. First, it turned out to insert the nucleus of the embryonic cell into the empty egg of the frog, and a little later - to grow the tadpole from the cell of the frog intestine.

Then came the turn of mammals. In 1984 Steen Villadsen insertedThe history of cloning the nucleus of a sheep embryo into a nuclear-free egg cell. The surrogate mother-sheep carried three clones-lambs. In the same way - from embryonic cells - chickens, sheep and cows have been successfully cloned.

Finally, in 1996, researchers at the Rosslyn Institute in Scotland created the first clone from the udder cage of a six-year-old sheep. After 276 attempts, the experiment succeeded, and Dolly the sheep was born.

After Dolly, many animals were cloned using this technology: a cow, a cat, a deer, a dog, a horse, a mule, an ox, a pig, a rabbit, rats and mice, a goat, a wolf.

Scientists have tried to clone monkeys, but it turned out to be not so easy. Only 10 years after Dolly was grown in a test tube stem cells rhesus monkeys, and the same number of live clones were created. In 2018, an experiment by Chinese scientists ended with the creationCloning of Macaque Monkeys by Somatic Cell Nuclear Transfer two long-tailed macaques: Zong Zong and Hua Hua.

Do clones really age faster?

Yes, at least some. Scientists speculate that this is due to chromosomes. All cells of the body passCloning through cycles of division, and the end portions of chromosomes - telomeres - are shortened. This is part of the natural aging process.

Dolly's chromosomes were shorter than those of the same age, and she lived half the life of the average sheep: 6 years instead of 12.

However, telomeres are shortenedAging of Cloned Animals: A Mini-Review not all clones. For example, in cattle, dogs and mice, the telomeres of clones are not less, and sometimes even more, than in control animals of the same age, but in sheep and wolves, on the contrary, they are almost always shorter.

Premature aging does not apply to goats: clones live 15 years laid by nature. The clones - cows, dogs and mice were also lucky. But cloned sheep, pigs and cats live less. As for the closest relatives of humans, monkeys, there is no such data yet. Since the first cloned macaques were bornCloning of Macaque Monkeys by Somatic Cell Nuclear Transfer recently, one can only guess how long they will live.

Can extinct animals be cloned?

After the movie "Jurassic Park" many hope that scientists will be able to clone a dinosaur, but it will forever remain a fantasy. Dinosaurs died out too long ago, so there was simply no tissue with DNA molecules left - only fossilized bones.

The cloning of mammoths and other animals of the Ice Age, the remains of which are periodically found in the permafrost, seems more realistic. However, at the moment this is almost impossible for several reasons.Mammoth Resurrection: 11 Hurdles to Bringing Back an Ice Age Beast:

• Cloning requires an intact nucleus with intact DNA, and even in the best-preserved remains, the genetic code is broken down into many parts. Scientists have to collect "letters" genomewithout knowing the exact sequence and focusing on the DNA of the next of kin, so it is impossible to predict what will happen in the end.
• To clone an animal, you need a surrogate mother. The closest relatives of mammoths are Asian elephants, therefore, only a female of this animal can become an egg donor and a surrogate mother for a mammoth. The procedure for taking an egg and planting it in the uterus will be very difficult, but even if everything goes well, not a pure species will be born, but a hybrid of a mammoth and an elephant.
• Scientists fear that even if cloning is successful, the animals will not have enough genetic diversity to create a new population.

Problems like these prevent the cloning of all extinct animals.

Can human tissues and organs be cloned?

In 2013, scientists from Oregon under the leadership of Shoukhrat Mitalipov succeededHuman Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer conduct therapeutic cloning of a person. Mitalipov and his colleagues took the nucleus of a somatic cell of a child with a rare genetic disease, placed it in a nuclear-free egg, and grew a blastocyte with stem cells.

In 2014, using the method of therapeutic cloning, scientists succeededHuman Somatic Cell Nuclear Transfer Using Adult Cells turn skin cells of 35 and 75 years old men into stem cells. In the future, progenitor cells can be used to grow any tissue and replace damaged areas and organs.

However, this method has problems: stem and cancer cells strikingly similarCloning. Some studies show that after 60 cycles of division, stem cells can accumulate mutations and lead to cancer.

There is evidence that stem cells from the amniotic fluid and placenta do not formStem cells derived from amniotic fluid: new potentials in regenerative medicine tumors. If these cells are used to create organs, many of the problems associated with cloning will disappear, from egg donation to the ethical side of using human embryos.

What about clones of entire humans?

In 2002, members of the Clonaid Raelin sect declaredCloning about the birth of the first human cloned - the girl Eve, as well as 12 other clones. Despite repeated inquiries from the scientific community and the media, Clonaid did not provide evidence of the existence of the clones.

In 2004, scientists from Seoul National University in South Korea announced the creation of a clone of a human embryo. However, an independent scientific committee found no evidence, and the study was withdrawn two years later.

What prevents people from cloning besides technology?

Human reproductive cloning causes a lotCloning fears. No one knows what biological and social consequences the cloning of people who have lived before or are still living on today might have. This can violate the principles of personal value, human rights and freedoms.

It is also not clear what to do with clones, if it turns out to create them: can they become part of society and how it will perceive their appearance.

Until all these problems are solved, human reproductive cloning is prohibited.Cloning: A Review on Bioethics, Legal, Jurisprudence and Regenerative Issues in Iran in 70 countries of the world, including Russia.

According to federal lawFederal Law of March 29, 2010 No. 30-FZ "On Amendments to Article 1 of the Federal Law" On the Temporary Ban on Human Cloning ", the ban will remain in effect until there is a law establishing the procedure for cloning organisms for the purpose of cloning humans.