Welcome to our new post! In this article, I will present to you some curiosities about cloning. The following topics will be addressed: What is cloning? How does animal cloning work? Types of artificial cloning, successfully cloned animals, how does therapeutic cloning work? Has any human been cloned? The advantages and disadvantages of cloning, and ethical questions about cloning. Get ready to learn amazing things about this procedure and amaze your friends with these interesting facts.
What is cloning?
The term encompasses various techniques aimed at generating a genetically identical copy of a biological entity. The first thing that comes to mind is the cloning of entire organisms, but genes, organs, and tissues can also be cloned. For the cloning of an extinct species that still has similar animals, an intact cell could be used or the entire genome of the extinct animal would need to be mapped to reconstruct its genome and the genome of the existing animal modified to transform it into that of the extinct animal. The ovum would then be implanted into a similar animal until the species had enough individuals to continue existing on its own. Studies have shown that both the meat and milk of cloned animals are not toxic to our bodies and generally do not show differences when compared to the same natural products. Clones are not only artificially generated in laboratories, but asexual reproduction also exists in nature, generating a new identical individual from a single cell of the parent. In mammals, something similar can be observed with identical twins. It's worth noting that in mammals, the DNA of the offspring is different from that of the parents, and even twins do not share the same DNA 100%.
Types of artificial cloning
There are 3 types of artificial cloning: genetic cloning, reproductive cloning, and therapeutic cloning. The difference between them lies in the outcome of the process. Genetic cloning produces copies of DNA segments or genes. Reproductive cloning produces entire individuals. And therapeutic cloning produces embryonic stem cells for tissue creation and reconstruction.
How does genetic cloning work?
The gene of an organism is inserted into a vector (bacteria, viruses, yeast cells, or plasmids), and then the necessary conditions are provided for the vector to multiply.
How does animal cloning work?
In reproductive cloning, a mature somatic cell of the organism to be cloned is needed. This sample will be inserted into an empty ovum or oocyte, meaning this cell had its own DNA removed and is now nucleus-free. The insertion of the cell's DNA into the ovum can be carried out in two ways. The first is to fuse the entire cells using an electric current. The second is to extract the nucleus of the somatic cell with a needle and inject it into the ovum. Initially, the first stages of embryo development occur in a test tube, and then the embryo is implanted into the womb of an adult female animal. This technique is called somatic cell nuclear transfer. The main challenge for these animals is to survive birth; those that survive are usually healthy. This technique has made it possible to increase the success rate and therefore reduce the mortality rate.
Successfully cloned animals
The most famous case of successful cloning is that of the sheep named Dolly in 1996. It took 277 cloned embryos to create her. But did you know that Dolly wasn't the first successfully cloned animal? In 1979, the first cloned mice were produced, and then cows, chickens, and sheeps were cloned. And now you might be wondering why Dolly is the most famous cloned animal? The cloning of this sheep was different from the previous ones; it was the first time that a mature somatic cell was successfully cloned. The previous cases involved injecting embryonic cells into an empty ovum. The San Diego Zoo maintains DNA samples from endangered animals. Using one of these samples, two banteng (a bovine native to Southeast Asia) were cloned. One of the animals (Noha) had an infection, and the other (Jahava) had to be euthanized. African wildcats have been successfully cloned using frozen embryos as a source of DNA. The first successfully cloned pet was a Maine Coon cat named Little Nicky, which honors its predecessor Nicky. The owner of the cat spent $50,000 on this procedure, which was carried out by Genetics Savings and Clone. This company had already cloned the first cat in 2001.
How does therapeutic cloning work?
They create a cloned embryo to produce embryonic stem cells with the same DNA as the original donor cell. This process helps to learn more about diseases and to treat them. The stem cells are removed from the embryo when it is still in the test tube during the blastocyst phase; at this stage, there are approximately 100 stem cells that make up the embryo. Further studies are needed to understand stem cells and cancer cells, as both have the ability to proliferate indefinitely. There are even studies that have shown that after 60 cycles of cell division, a stem cell can become a cancer cell.
Has any human been cloned?
Some studies and institutions have claimed to have achieved it, but they have never presented evidence of it. Cloning of humans and primates is more challenging than with other mammals because the correct cell division requires two proteins called fusiform. These proteins are located very close to the nucleus in human eggs, and during the process of removing the nucleus from the egg, they can be damaged. Other mammals have this protein located throughout the egg.
Scientific applications for cloned animals
Scientists who cloned Dolly conducted a study to alter the milk production of sheep and add a protein for blood clotting. The goal of this study is to purify this protein in the future and provide it to people with blood clotting deficiencies. That's why these modified sheep were cloned. Another significant contribution of cloned animals to science is that, being genetically identical, they should react in the same way to drugs. This would allow for more effective preclinical drug testing.
Advantages of cloning
DNA from prize-winning bulls that can be valuable to farmers can be preserved. Animals with better milk or lean meat production or other desirable characteristics can be cloned. Recover lost animal diversity over the years. This would allow for interaction with these specimens, research, and observation. We can already see endangered animals in several zoos, but in the future, there could even be zoos with animals that are currently extinct. Being able to appreciate these incredible animals that ended up extinct due to climate or hunting reasons.
Disadvantages of cloning
The main challenge when cloning animals is the cost of the procedure. When it comes to extinct animals, this cost increases due to the difficulty of finding specimens that can be used as evidence. As they are cloned from adult cells, the telomeres of the chromosomes are shortened. This is normal as organisms age, but cloned animals have shorter chromosomes compared to normal individuals of the same age. These animals still have a high mortality rate. It is thought that this is due to a resistance of the donor egg that prioritizes genetic memory over replaced genes. They can also present defects in vital organs. Due to the high mortality rate, there is an ethical problem of bringing animals to life that may die, without knowing if they will be healthy or not.
Some of the animals that became extinct a long time ago would not adapt to the current condition of our planet; a way to not only replicate but also evolve their genome or provide a more suitable habitat would be needed.
Cloning produces genetically identical individuals, so it's not possible to maintain the necessary diversity for species survival. Cloned animals, even with the same genetics as the original animal, may have different phenotypic characteristics. In some species, genes responsible for coat color are randomly activated and deactivated. Environmental conditions also influence animal appearance. Cloned animals can be born larger than normal. They can age prematurely and have immune problems.
Ethical questions about cloning
Given the high mortality rate, many question whether it is ethical to bring animals to life that do not survive the experiment or even have health problems. Others defend this practice because if the procedure is never done, it cannot be perfected, and therefore this problem cannot be solved.
Some see cloning as an opportunity to reduce costs for future gastronomic or hunting experiences. But there is also the problem that animals are living beings, and raising animals in laboratories with the sole purpose of killing them does not seem ethical. On the other hand, it would solve the problem of overfishing and the risk of extinction of some of these specimens.
Many question the practice of breeding these animals for tourism and keeping them in captivity because it would not allow them to be in their natural habitat or live freely.
If the DNA of these extinct animals is combined with that of their current relatives, will the cloned animals truly be the return of the extinct animals or simply a variation of them? Some scientists believe that if the missing genes are not exclusive characteristics of this species, they could be brought back.
Could these animals have a negative impact on our planet's ecology?
Conclusion
Cloning will continue to evolve, starting from current specimens, until it becomes possible to clone animals that recently went extinct, and then evolving to clone animals that have been extinct for longer periods.
Currently, only DNA up to 1 million years old can be cloned, so animals that lived longer ago cannot be cloned. Cloning could bring these animals back and preserve diversity, as long as animals are treated with respect and provided with dignified conditions. This practice, along with current animal preservation measures, could help many species.
Bringing back extinct animals is possible, but we are still far from achieving this due to the difficulty not only of cloning these animals but also of bringing the necessary diversity for them to mate and produce healthy individuals with biological diversity that do not share the exact same genetic code.
📚 Data source:
https://www.bbc.com/mundo/vert-fut-43944682
https://www.genome.gov/about-genomics/fact-sheets/Cloning-Fact-Sheet
https://www.abc.es/ciencia/abci-cinco-anos-tendremos-dinosaurio-201211080000_noticia.html
Horner et al. Nonpathological inflammation drives the development of an avian flight adaptation. May 1, 2023. DOI: https://doi.org/10.1073/pnas.2219757120
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