Cloning is actually a way of asexual reproduction under artificial intervention, but asexual reproduction is not necessarily considered cloning, because there are many ways of asexual reproduction in nature.
For example, asexual spore reproduction, split reproduction, budding reproduction, etc., even some animals can also perform parthenogenesis, that is, egg cells can develop into individuals without sperm.
The individual or group cloned under artificial intervention has exactly the same set of genetic genes as the donor cell, and it can be said that this cloned group has the same appearance as the mother, but the behavior and thought are different.
The birth of dolly, the world's first cloned sheep on July 5, 1996, caused a huge sensation in the world's scientific, social, and religious circles.
For a time, this little lamb became a global star, presumably everyone has heard about it, and the birth of Dolly represents that artificial cloning biotechnology has entered a new era, which has a milestone significance in the development of cloning technology.
However, any technology has two sides, just like nuclear energy, cloning is no exception, since we humans can clone sheep, then the clones that have appeared in science fiction works before have naturally become a reality.
However, human cloning poses serious social and ethical problems, because your clones have the same genes as you and are likely to look exactly like you.
This clone is exactly your copy, but they are also a separate individual, and they have different ideas from you, do you say they should be called your brother/sister, or daddy/mom? Or are they just you? How do you face and deal with this complex relationship?
If human beings use such technology to clone themselves, then the whole society is not in a mess. So Dolly's birth really makes people feel that some science is really dangerous.
In fact, the cloned sheep Dolly is not the first clone under human intervention, before that we also cloned some creatures such as North American leopard frogs and carps.
However, the cloning technique used before Dolly was the transfer of embryonic cell nuclei, which is relatively simple and has a high success rate, and the cloned individual is actually a descendant of the embryonic cell donor, not a biological replicator.
The picture above is the process of embryonic cell nuclear transfer and cloning, the genetic material of an organism is mainly contained in the nucleus, we first extract the fertilized embryonic cells from an organism, then extract the nucleus, and transfer the nucleus into the denucleated oocyte (from another individual).
Then, through the method of electrical stimulation, the embryonic nucleus and the derupated oocytes are fused with each other, and the new embryo is cultured to form a new embryo, and the new embryo is transferred to the uterus of another female individual again, so that it begins to develop into a complete individual.
In this way, it is possible to clone the offspring of many embryonic egg cell nuclear donors, and these offspring have the same genes with each other. If this technology is applied to people, there will be many brothers and sisters who are exactly the same as your genes and look basically the same, which can be said to be difficult to distinguish by appearance alone.
But your relationship is still brothers and sisters, and you have three mothers in common and a father.
Dolly's birth process is very similar to the above process, but the only difference is that Dolly's nuclear donor is not an embryonic cell, but a breast cell from a 6-year-old white-faced sheep, that is, a normal somatic cell.
The receptor denucleated oocytes came from a black-faced sheep, fused the two in the same way and implanted into the womb of a third female sheep, and finally Dolly was born.
That is to say, Dolly has no father, only three mothers, it is a complete replica of the white-faced sheep, through genetic determination dolly and white-faced sheep have exactly the same genetic material.
In contrast, this method of cloning is much more difficult and has a very low success rate, and the clone of such an individual cell may die hundreds of juveniles.
Because many individuals cloned in this way will have congenital diseases, deformities, and will die very early in life. Therefore, researchers who clone Dolly have also said that Dolly is simply a miracle.
However, Dolly's success also broke a misconception in the biological world for a hundred years, before Dolly's birth, people had always believed that somatic cells had been highly differentiated and matured, and it was impossible and impossible to form all types of cells and complete embryos in the body again.
But it turns out that the individual somatic cells of animals have such an ability that they can once again differentiate into various types of cells and organs in the organism. Of course, people are no exception.
Through your somatic cells, you can copy an embryonic cell that you don't need to be fertilized at all, and such a mysterious thing has become a reality, which is why Dolly was sensational around the world at that time, and people immediately felt that they had entered the era of cloning.
So why does cloning seem to have stopped so much in recent years?
It is true that we rarely hear such reports, and it seems that people have slowly become calmer in the frenzy of the time. To be honest, at present, there is really the ability to clone a you, but who dares to attack people? This is a big deal against the world.
No one wants to be scolded by history, and apart from ethics, the clone is not a perfect individual. Dolly is a prime example.
The average sheep live between 11 and 12 years, but Dolly has only lived about 6 years, and there is a problem here, although Dolly was born as a baby lamb, but it is a replica of a 6-year-old white-faced sheep after all.
How old was Solitaire when she was born? We all know that there is a Havreck upper limit on the number of cell divisions, that is, the number of divisions is certain, Dolly was born from the number of maternal cells that have divided by half, and Dolly is exactly half the age of life.
This seems to confirm the Havreek upper limit, which may also be the cause of premature aging of clones.
In addition, Dolly's life has also been plagued by many diseases, and she has been replaced by many old age diseases at a young age, such as arthritis, and she died of lung infections in her prime, and finally she can only be "happy" to die.
After Dolly, many clones like Dolly were born around the world, and the number of premature deaths and deformities was very high, and these animals would face many disease problems in their lives, of course, premature aging was inevitable.
As for the process of cloning, or what problems exist in this breeding method itself, which has led to a series of problems in the clone, we are not very clear at present.
However, the relevant research has been going on, but after a bout of madness, it will always calm down, and this technology is not quite mature as everyone thinks, so it is rarely mentioned now.
I believe that in the future, even if researchers solve the above problems, they will not be used to directly clone people, which is completely worthless, but I also estimate that no one wants to clone themselves, after all, the appearance of another self will bring you a lot of trouble.
We can't clone people, but we can clone our own organs! I believe you have seen that in 2019, Japan approved the domestic "hybrid embryo" experiment.
In fact, this experiment also uses basically the same way to implant human stem cells into animal embryos to achieve the purpose of cloning human organs. This is a boon for humanity.
Therefore, no matter which technology can benefit mankind or destroy mankind, it depends on how we use it, it depends on who has mastered the technology, and people with incorrect mental skills will certainly not be able to do good.