When on July 5, 1996 was born Dolly, the cloned sheep, many celebrated the taking of human control over DNA as a preview of future developments, such as in organ transplantation area.
Others, however, expressed the fear of a new world of identical beings created as spare parts.
In fact, none of this has happened in 20 years.
Human cloning, a complex, risky and ethically questionable process, was finally replaced by other technologies as a source of regenerative medicine.
"It happened what was expected," said Rosario Isasi, of the Institute for Bioethics and Health Policy at the University of Miami.
"There was a moment of euphoria:. Some thought that finally would be able to better understand the mechanisms of disease, use it as a treatment for infertility is not what happened," he told AFP.
Dolly, the most famous sheep in the world, was the first mammal cloned using a technique called somatic cell nuclear transfer (SCNT).
It involves removing the nucleus of the cell with its corresponding DNA in a cell other than an egg or sperm - a skin cell, for example - and implant it into an egg not fertilized, which previously cored.
In the case of Dolly, the cell was removed from a mammary gland.
Once the transfer, the egg reprograms an embryo from the DNA that begins to develop as a child of only one parent.
There is no information to date of a cloning such humans.
risk of escalation
There is a global opposition to human reproduction by cloning.
In addition to the ethical objections and human rights to create human beings as photocopies, there is also a safety issue.
Only a few cloned animals survived the birth and many recorded later health problems.
Experts believe that the moral opposition to cloning as a reproductive technology has overshadowed the potential benefits of the technique in regenerative medicine area.
In general, people fear that scientists can not resist the temptation.
"Once we define the limits of protection, there is no way to divert to reproductive applications," said, however, Isasi.
Still, "many people fear to happen a slip, a light thing to another, until something bad happens. This is the main concern that has prevented the use of technology," he adds.
Investments in research on cloning decreased and few countries - including Belgium, China, Israel, Japan, South Korea, Britain and Singapore - allow the creation of embryos for experimental purposes. The United States is not something explicitly illegal.
In therapeutic cloning, scientists get stem cells from an embryo in its early stages or blastocyst, an aggregate of between 100 and 200 cells.
Target these cells for specialized development of liver or blood cells, for example, can help cure certain diseases or repair affected organs.
How are created from the patient's own DNA, the risk of transplant rejection is drastically reduced.
But producing stem cells in this way involves destroying embryos, another moral dilemma.
And while some scientists have managed to create stem cells from SCNT, none managed to get to develop as a functional human organ.
Dispense embryos
Cloning may not have found a direct application in medicine, but stimulated the development of other technologies, such as induced pluripotent stem cells.
The technique is to develop specialized cells causing reassemble the earlier stages of development, allowing dispense with use embryos.
The technique, awarded a Nobel, has dominated the attention of regenerative medicine, but is not yet fully established that the resulting cells to function the same way that stem cells obtained from embryos.
Another branch is the transfer of genes through the mitochondria, which lets you deploy DNA in a healthy egg to create an embryo free of abnormal mutations that can affect the mother.
Aaron Levine, bioethics expert at Georgia Tech, said the biggest impact of cloning on human health probably comes from animals bred specifically to produce organs, tissues or biological products that would not be rejected by the human immune system.
"I believe that human cloning will disappear. There simply is not enough demand, there is not much anyone can do with cloning you can not do otherwise," opines.
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