Is human cloning possible? How does the copy differ from the original? What’s the point? Embarrassing questions about the most discussed topic in modern biology
On January 24, it became known that Chinese scientists successfully cloned primates for the first time using the method used in the experiment with the famous Dolly sheep. Cloning is one of the most surprising and discussed topics in modern biology. Medusa asked Konstantin Severinov, a doctor of biological Sciences, Professor at the SKOLKOVO Institute of science and technology and Rutgers University, to answer basic questions about cloning.
What is cloning?
Cloning is a process or technology for obtaining clones. A clone is an organism that is genetically identical or almost identical to another. Identical twins are clones of each other, since both originated from the same fertilized egg. Plants created by vegetative propagation — such as strawberry bushes propagated by whiskers, are also clones.
But a child is not a clone of its parents. Every human cell has a double set of genes: one set from the father, the other from the mother. At conception, both the father and mother pass on only half of their genes to their offspring — one set each. In this case, which of the duplicated genes of the father and mother is transmitted to the offspring is determined by the case. Since the versions of the genes available to the parents differ slightly from each other, the offspring also differ from the parents. From the point of view of biology and evolution, this is good, because genetic diversity increases. The more diverse the population, the more likely it is that when environmental conditions change, carriers of certain combinations of genes will survive and leave offspring.
However, in the context of commercial agricultural production, for example, diversity is a source of problems. If you want to maintain a herd of Angus with certain properties, the need to obtain steers by sexual reproduction inevitably leads to the fact that not all the offspring will be the same as the original animals, and some of the animals will have to be culled. Cloning could solve this problem (actually, in the case of strawberries, the problem is solved, but cows, alas, do not reproduce with whiskers, everything is more difficult there).
How did scientists breed Dolly the sheep? They took the cells of a female and a male and somehow connected them in a test tube?
Dolly the sheep was “made” as follows: they took a sheep’s udder cell and the genetic material of this cell was “planted” in an egg taken from another sheep. In this case, the own genetic material from this egg was previously removed. Note that the resulting egg had a double set of genes — the same as in the udder cell. This means that fertilization of such an egg was not required! This egg was planted in the uterus of a third sheep, which carried and gave birth to a sheep — Dolly.
The sheep that gave birth to Dolly is a surrogate mother: it is not genetically related to Dolly. The sheep from whose egg Dolly developed is not related to her, since she and Dolly have almost no common genes. But the sheep, from the udder cell which took the genetic material for planting in the egg, is the” genetic mother ” of Dolly (and Dolly, in turn, her clone). Their genes are almost identical. Dolly didn’t have a father — from a genetic point of view, it was the father of Dolly’s genetic mother, but it turns out that he was also her grandfather.
How does a cloned copy differ from the original? Are they like twins or not exactly?
Identical twins occur when a developing embryo splits into two (or four) embryos and each of them then independently develops into an adult organism in the womb. In General, clones are very similar to identical twins, only they are not born at the same time, but are carried at different times by different mothers and can appear after the biological death of their original. A clone is created based on a genetic program-the DNA contained in a cell of an adult or deceased organism.
All the cells in our body are the descendants of a fertilized egg that originated at the moment of our conception. But this does not mean that the cells of our body are completely identical. Every time a cell divides, genes, DNA molecules, are copied inside it. When copying, errors and mutations always occur — just as typos occur when rewriting a long text. When a cell in an organism like a human or a sheep divides, about 50 new mutations that did not exist in the DNA of the parent cell spontaneously appear in the DNA of the daughter cells. That is, the genes of the udder cell from which Dolly was derived are not actually completely identical to the genes of the egg cell from which her mother developed.
Since Dolly’s time, have there been many similar cases where scientists have cloned animals?
After Dolly, they cloned fish, frogs, rodents (rats and mice), dogs and cats, pigs, horses and cows. On January 24, it became known about the cloning of primates-long-tailed macaques. In General, this procedure is applicable to any body, just in each case, a lot of time is spent on the selection of optimal conditions.
When will they learn to clone people? Or have you already learned?
There are no fundamental problems in cloning people. If you set such a task, you will need to optimize experiments on planting genetic material from adult cells in an egg that is devoid of its own genetic material. But cloning people is forbidden because of ethical issues.
How can cloning help humanity? Spare liver? Clone army? Experiments on clones?
Both with the clone army and with experiments on them, there are unsolvable ethical problems, as well as some practical difficulties — so they will not do so.
Take two twins. Before you take the liver of one of them for another, or perform some sharp experiment on one of them, reasoning that the second (i.e., the clone) will remain, you will have to get the consent of the first. He or she can refuse, because they are individuals and have the same rights as other people. So, if you created your clones, then they, becoming people, and not a piece of meat in a test tube, will also probably have views on their liver that will be different from yours. So with the liver, or more broadly, the source of organs, the problem is that we don’t know how to get a liver clone separately — in this case, there would be no ethical problems.
About the clone army. If you created clones of the conditional Deputy Nikolay Valuev, because he is big and intimidating looks, then to get them in a “ready-to-use” state, you, or rather, their surrogate mothers will have to raise them, as they raise all people, up to 20 years. During this time, political regimes may change — and the need to frighten today’s enemies will disappear. In addition, you can not exclude that some of the clones decide to become intellectuals and do not want to play your games, and want, for example, to study molecular biology. And getting them to do something just because they’re clones of some uncle who may have died a long time ago will be difficult against their will. It is much easier to recruit existing people into your ranks.
Can cloned organisms have offspring? Will they have any special features because they are descendants of a clone?
Under the right conditions, cloned organisms will not differ from naturally occurring organisms and will be able to produce offspring. Another question is that if you completely exclude sexual reproduction and switch to clonal, then over time in the generations of clones will inevitably accumulate mutations that reduce the fitness of the body. Sexual reproduction — the exchange of gene combinations to create new combinations-is necessary to maintain the diversity and stability of species for a longer time in an unpredictably changing environment.
Why do many people think that cloning should be banned? What’s dangerous about that?
Cloning of farm animals is not dangerous, and if the technology is developed accordingly, it is convenient and profitable. The problem arises if you start thinking about human cloning. It’s easy to deal with an animal: you’ve cloned it, raised it, or eaten a steak, for example, and you can be sure that its quality will be the same for decades. We don’t usually care about whether the cow that became the source of the steak was a person.
We perceive people as individuals. Personality is formed not only by genetics, but also by upbringing, the time and place in which a person was born and formed, various random causes and encounters, and other factors. Therefore, human clones will not be the same personalities (for example, identical twins are similar to each other in appearance, but are certainly different people with their own lives, addictions, different dates, places, and causes of death). Therefore, as long as there are no state regimes in which people can be used for conditional steaks, cloning people is not dangerous. It is dangerous if such modes become possible.