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

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

In the long term, this will allow replacing damaged cells, but the ethical issue remains open.

What is cloning?

Cloning Cloning is the creation of genetically identical copies of living organisms or their fragments. Different biological material can be cloned: individual cells, tissues, organs and whole organisms.

What are the types of cloning?

Molecular cloning

Using this method, scientists isolate genes of interest with Gene Cloning, 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 are derived: plants that are resistant to pests, animals that are immune 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 the 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 used by Tissue 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 species allows Cloning to 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, it is implanted into the uterus of an individual 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 obtained 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 an empty frog egg, and a little later - to grow a tadpole from the frog intestinal cell.

Then came the turn of mammals. In 1984, Steen Villadsen inserted The History of Cloning the nucleus of a sheep embryo into a nuclear-free egg. 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. It was only 10 years after Dolly that rhesus monkey stem cells were grown in a test tube, and the same number of live clones was created. In 2018, an experiment by Chinese scientists ended with the creation of Cloning of Macaque Monkeys by Somatic Cell Nuclear Transfer by 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 go through Cloning cycles of division, and the ends of the chromosomes - telomeres - are shortened. This is part of the natural aging process.

Dolly's chromosomes were shorter than those of one-year-olds, and she lived half the life of an average sheep: 6 years instead of 12.

However, not all clones have telomeres. Aging of Cloned Animals: A Mini-Review. 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 born Cloning of Macaque Monkeys by Somatic Cell Nuclear Transfer recently, it is anyone's 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 this will forever remain a fantasy. Dinosaurs became extinct too long ago, so there is simply no tissue with DNA molecules left - only fossilized bones.

It seems more realistic to clone mammoths and other animals of the Ice Age, the remains of which are periodically found in the permafrost. However, at the moment, and 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 the "letters" of the genome, not knowing the exact sequence and focusing on the DNA of the next of kin, so that 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 this prevent the cloning of all extinct animals.

Can human tissues and organs be cloned?

In 2013, scientists from Oregon, led by Shoukhrat Mitalipov, managed Human Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer to carry out therapeutic cloning of a human. Mitalipov and his colleagues took the nucleus of a somatic cell from a child with a rare genetic disease, placed it in a nuclear-free egg cell, and grew a blastocyte with stem cells.

In 2014, using the method of therapeutic cloning, scientists succeeded in using Human Somatic Cell Nuclear Transfer Using Adult Cells to turn the skin cells of men 35 and 75 years old 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 cells and cancer cells are strikingly similar to Cloning. 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 amniotic fluid and placenta do not form Stem cells derived from amniotic fluid: new potentials in regenerative medicine of 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 announced to Cloning 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 is stopping people from cloning apart from technology?

Human reproductive cloning raises many cloning concerns. No one knows what biological and social consequences the cloning of people who have lived before or are still living on might have. This can violate the principles of personal values, human rights and freedoms.

It is also unclear what to do with clones, if it turns out to be possible to create them: whether they can become part of society and how it will perceive their appearance.

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

According to the Federal Law Federal Law of March 29, 2010 N 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 a law appears establishing the procedure for cloning organisms in purposes of human cloning.