On February 27, 1997, it was revealed to the world through the journal Nature that Scottish scientist Ian Wilmut of the Roslin Institute in Edinburgh successfully cloned a sheep through a procedure that involved using a cell taken from a sheep's udder, fuse it with an egg that had previously had its nucleus removed and then implant it in the uterus of a third sheep.
This artificial egg grew and after 148 days Dolly was born, a healthy sheep that had been a genetic copy of the mammary cell donor sheep, but at the same time had no genetic relationship with either the recipient cell or the sheep. who gave birth to Dolly. From that precise moment they began great debates about this event with voices in favor and against it; the catholic church for example was totally against this type of procedures while some members of the scientific community admired and supported it as a means to find solutions to several of the diseases that afflict human beings.
From the scientific point of view, cloning can bring many benefits to improve the quality of life of the human being, such as the production of organs that serve as a transplant, obtaining cells to cure or treat deadly diseases, improving productivity and quality of livestock., the production of medicines, among others.
But on the other hand, this type of procedure could also bring great harm to the human being, such as genetic manipulation to create a perfect race, as well as replacing sexuality as a method of reproduction so that science plays the same role through procreation. of new human beings with desirable characteristics. (Cambra, 2016)
In this article we will review the general concepts related to cloning as well as the positions in favor and against this scientific advance.
What is cloning?
The word "clone" is a term that was adapted to Spanish from the word clone in English which is derived from the Greek meaning "shoot" or "sprout."
Cloning can be defined as the process of obtaining one or several individuals from a somatic cell or from a nucleus of another individual, in such a way that the cloned individuals will be identical or almost identical to the original. It can also be defined as a form of asexual reproduction whereby genetically identical individuals are created. Another definition indicates that cloning is those techniques to achieve, from a vital unit (a living cell or organism), by asexual multiplication, individuals genetically identical to each other. And finally, how to isolate and multiply in a test tube a certain gene or, in general, a piece of DNA, this from the point of view of genetic engineering.
It is also conceptualized as the scientific procedure that consists of taking the genetic material of an organism to obtain an identical one, called a clone. Through cloning, there is no union of eggs with sperm. 11 In the context to which we refer, cloning means obtaining one or several individuals with the same genetic material, from a somatic cell or from a nucleus of another individual, so that the cloned individuals are identical or almost identical to the original.
Despite the fact that the term cloning is believed to be new, the reality is that it was known since the last century but for the plant kingdom, where a slice of the plant to be copied was planted to obtain a different plant but that genetically was the same to the one of origin. This is done for various single-celled animal species and organisms. In summary cloning is a type of asexual reproduction. (Navarro & Montes, 2002)
Chromosomes and DNA.
A chromosome is a tiny threadlike structure that is made up of nucleic acids and proteins and is present in plant and animal cells. Chromosomes contain DNA that in turn is divided into small units called genes that determine the hereditary characteristics of the organism. Organisms, whether animal, plant, or human, have a fixed number of chromosomes; the human being has 23 pairs of chromosomes which are donated 50% by the parents and the remaining one by the mother.
The name chromosomes means "colored bodies", due to the intensity with which they fixed certain dyes when stained to be able to observe them under a microscope. The chromosomes repeat in the cell forming, as already mentioned, 23 pairs of chromosomes. Since the chromosomes contain the genes that are responsible for the genetic information of human beings, in almost almost all the cells of the body we can find the complete complement of chromosomes necessary to re-create that body in its entirety. (Couple, 2016)
The genes
Living organisms are made up of microscopic units that group together to form cells. These cells have a nucleus inside, inside which is a macromolecule that is in charge of genetic information; The latter is made up of deoxyribonucleic acid (DNA), which at the same time is made up of two chains linked together and wound in a spiral. The different portions of this molecule that are responsible for a specific hereditary characteristic are called gene.
Genotype
Genotype is called the set of inherited genes which provides the necessary information for various traits to be produced. These traits will be influenced by the external environment, such as exercising will affect the muscular structure of a certain person. This interaction with the environment results in the “Phenotype” that has been the set of characteristics external to the individual and can be sensory appreciated.
Cloning methods.
There are two cloning methods: natural and artificial. The first occurs without the participation of man and may be due to spontaneous biological development, an example is the identical twins that come from an egg fertilized by a sperm that in the early stages of development is divided into two genetically identical individuals. In the second, man manipulates the genetics of an organism applying scientific and technical advances related to assisted reproduction. This type of cloning has been done for a long time with vegetables.
Types of cloning
The types of cloning are:
- The partitioning (fission) of early embryos: It is carried out as an analogy with natural twinning. In this type of cloning, individuals are very similar to each other, but different from their parents. For this type of cloning, it is preferable to use the expression Artificial relation, and it should not be considered as cloning in the strict sense. enucleated zygotes. The "origin" or "progenitor" of the clones is the embryo or fetus. The true cloning: it consists of transferring nuclei from cells of individuals already born to ovules or zygotes without nuclei.It gives rise to individuals almost identical to each other (except somatic mutations) and very similar to the donor (from which they differ in somatic mutations and in the mitochondrial genome, which comes from the recipient egg). The nucleus comes from a born individual and is transferred to an enucleated ovum or zygote, and the embryo implants in the uterus.
Example of successful cloning
- Dolly the sheep: in this case the donor nucleus of an unidentified cell was taken from the udder of a 6-year-old sheep of the Finn Dorset breed. Then the embryo was implanted into a female Scottish Blackface breed. A low success rate was obtained: 430 eggs, from which 277 reconstituted eggs were obtained, which were cultured separately for 6 days. 29 "normal" blastocysts were transferred to recipient females. The only success was Dolly. Some were dead fetuses or neonates, or with developmental disorders. In mice: the first cloned mouse was born on October 3, 1997 and was called Cumulia; the procedure was carried out by Japanese scientists who used a species of laboratory mice. Soon after, this same Japanese team reported cloning mice from stem cells of adult mice.Cattle: Nuclei of epithelial cells were obtained from the oviduct, cumulus oophore, epithelial, muscle. Cattle Cattle: Nuclei of cells were obtained as in the previous example. Roslin-PPL new method of double nuclear transfer, with the birth of five piglets, with two subgroups of three and two that were clones with each other and with respect to the corresponding donor. Their names: Millie, Christa, Alexis, Carrel and Dotcom.A new method of double nuclear transfer was obtained by the Roslin-PPL group, with the birth of five piglets, with two subgroups of three and two that were clones with each other and with respect to the corresponding donor. Their names: Millie, Christa, Alexis, Carrel and Dotcom.A new method of double nuclear transfer was obtained by the Roslin-PPL group, with the birth of five piglets, with two subgroups of three and two that were clones with each other and with respect to the corresponding donor. Their names: Millie, Christa, Alexis, Carrel and Dotcom.
Cloning history
Genetic cloning has been developing for more than forty years with research in different areas of knowledge such as genetics and reproductive biology. In 1952 frogs were successfully cloned and the question was raised whether it was possible to do the same in superior animals such as mammals from an adult animal. Later in 1970 further research followed and in 1981 cloning of a mouse occurred. The same investigation was continued in mice but was not successful. Already in 1986 the physiologist Neal First of the University of Madison in the United States managed to create the first cow by cloning. He did this by collecting a cell from a six-day-old bovine embryo and fused it with an fertilized egg with an electric shock.The resulting embryo was implanted into a cow, from which a normal calf was born.
As early as 1993, at George Washington University, it was possible to separate blastomeres (each of the primitive cells of the embryo) from human embryos, which maintained the capacity of cell division for a certain time, but at no time were these embryos transferred to the maternal uterus due to the ethical consequences that this experiment would cause.
Later in previous studies, cell transplantation had many failures because in both amphibians and mammals there was incompatibility in the cell cycle between the donor and the recipient cell, leading to the appearance of chromosomal alterations that impede embryonic development. It was then that Dr. Ian Wilmut and his team were able to solve this obstacle using a cell obtained from a sheep's udder by fusing it with an egg that had previously had the nucleus removed, which was implanted in the uterus of a third sheep. The artificial egg grew and after 148 days it became Dolly. The product obtained is a genetic copy of the mammary cell donor sheep, but has no genetic relationship with either the recipient cell or the sheep that gave birth to Dolly.
Cloning in humans
According to the British scientist Ian Wilmut, who led the cloning of the sheep "Dolly", cloning can be very useful for medicine but nevertheless opposes the cloning of human beings. According to him, these types of practices would be of great help to treat infertility and some diseases such as muscular dystrophy or Parkinson's, therefore all people and their families could clearly benefit from research with cloning technology, but not never includes the cloning of a human being
At the same time, the cloning technique would be very useful to regenerate the spinal cord in those who suffer paralysis; achieve the production of drugs, vaccines, proteins to combat diseases such as hemophilia; in addition, bone marrow could be cultured in test tubes, to cure anemia. And other diseases such as cancer, diabetes or other ailments that necessarily go through research with human cells.
Stem cell cloning
Currently, many scientists are interested in conducting research aimed at cloning stem cells to contribute to the treatment of various diseases such as Parkinson's and cancer.
What are stem cells?
Stem cells are cells with no function of their own that have not yet become cells of a specific tissue. They differ from the rest of the other body cells because when they divide they present the following properties:
- They generate new copies of themselves indefinitely. They generate new cells that, when properly manipulated, can be transformed into the different tissues of which the human body is composed. They have the ability to colonize and repair diseased tissue or organ by replacing cells. sick from healthy cells.
It is from stem cells that human beings develop once the ovum and sperm unite and are the ones that give rise to the tissues and organs of our body. All the organs and tissues of the human body have a small reserve of these cells that are what allow their maintenance and repair. (Genetics, 2016)
Purpose of stem cell cloning
The goal of stem cell cloning is to appropriately combine all knowledge of genetics, medicine, physics, chemistry, molecular biology, cell engineering, and other related branches of science so that from one or Very few cells can be designed and produced as many cells as necessary to repair the damaged tissues, organs or structures of our body. This is called regenerative or reparative medicine.
By doing this in Parkinson's disease, for example, the failed nerve cells could be replaced by new nerve cells, and the person suffering from the disease could heal.
On the other hand, heart cells that are damaged due to heart attacks or heart failure could be replaced by new heart cells and the person could heal.
In addition, spinal cord injuries caused by tumors and accidents could be repaired. People with diabetes may have insulin-producing cells transplanted into their pancreas and heal.
The same could happen in diseases such as: cancer, cystic fibrosis, degenerative diseases such as Alzheimer's, etc.
Scientific advances on stem cell cloning
On May 16, 2013, a group of scientists from the University of Oregon led by Dr. Shoukhrat Mitalipov published in the journal Cell that they had cloned stem cells from the skin cells of an eight-month-old boy. who had a genetic disease.
To do the cloning, they created embryos, taking the DNA from an egg (so that it was hollow) and then replacing it with the DNA from the skin cell. The baby's DNA was the only genetic material that was used.
Using chemicals, the egg began to divide in the same way that a fertilized egg does. Then, after several days, embryos genetically identical to the baby emerged, from which the stem cells were taken.
These investigations are controversial because to use stem cells, the embryo - a group of cells that can develop as a human being - must be destroyed, even if they are the remnants of in vitro fertilization.
However, Dr. Mitalipov argues that the embryos created in his study, from skin cells and eggs, do not generate babies. That would have required additional technology and was not part of the investigation.
Ethical considerations on cloning
Dolly's emergence as a palpable example that mammals can be cloned, sparked debate over the possibility that the same may be true for humans as well, which runs counter to human dignity. The cloning of human beings is ethically criticized because the sense of human sexuality is not respected and for a great characteristic that differentiates us from other beings: that we are unique and unrepeatable.
In the genetic field, species evolve constantly and permanently, in such a way that successive generations take advantage of past variations, adapting them to their new needs, and then genetically transmitting them to the next generation and on. If cloning is allowed, the genetic material is truncated, which would pose a serious risk to the survival of the species.
When creating human beings through cloning, the act of love of the parents is replaced by a technical act of a third party, which is the one who through scientific procedures gives the initial push to the new life. In these cases a human production would be carried out and not a human procreation. Furthermore, it is not ethically accepted that people are reduced to things, created by a third party under the condition of a mass-produced object, as if it were a product. For this reason, there is much worldwide rejection towards the cloning of human beings. Human beings must be protected to safeguard the integrity of the species as a value in itself and the dignity of each of its members,since he has a specific genetic identity and his personality cannot be reduced solely to genetic characteristics and be treated as an object.
However, in the event that the cloning of human beings were carried out, the identical replication would be only on a physical level because on a psychological and mental level it would be a completely different person. (medicine, 2002)
Ethical considerations on cloning stem cells
The most discussed ethical aspect regarding cloning stem cells is that in order to carry out this procedure it is necessary to kill many embryos from where the cells are to be obtained. Said embryos can come from in vitro fertilizations as a procedure for assisted reproduction or can be obtained in vitro with the sole purpose of experimenting with them or created by cloning, a process that corresponds to what has been called "therapeutic cloning", contrary to the "reproductive cloning", whose objective is to create an embryo to obtain a human being. (Landau, 2013)
Obtaining embryos in vitro for the sole purpose of research is ethically unacceptable to many who consider that human life begins the moment the embryo is produced. However, people who are in favor of cloning stem cells assure that it is not clear that the life of a human being begins at the moment of fertilization, so it is debatable that individuality begins with fertilization. (Hernandez P., 2016)
conclusion
Cloning is definitely a scientific advance of our time that is worth analyzing, however, it must also be seen from an ethical perspective because although it can be used as a method to cure various diseases that afflict humans, it could also be counterproductive if handled improperly.
Bibliography
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Couple, EI (2016). University of Granada. Obtained from
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Thanks
To the Technological Institute of Orizaba for giving me the opportunity to train professionally and to Professor Fernando Aguirre y Hernández for all the knowledge he has shared in his subject Fundamentals of Administrative Engineering to learn and improve my abilities to write quality scientific articles.
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