Tan Gek Mui
Khoo Huai Shin
Tan Shuik Yin
Human cloning is the creation of a genetically identical copy of a human or human cell. The term is generally used to refer to artificial human cloning. Human cloning will be used to refer to the application of somatic nuclear transfer technology to the creation of a human being that shares all of its nuclear genes with the person donating the implanted nucleus.
The three types of cloning technologies are recombinant DNA technology, reproductive cloning, and therapeutic cloning.
Recombinant DNA Technology or DNA Cloning
Recombinant DNA technology is a process which is the transfer of a DNA fragment of interest from one organism to a self-replicating genetic element such as a bacterial plasmid. The DNA of interest can then be propagated in a foreign host cell. A particular gene often uses bacterial plasmids to generate multiple copies of the same gene. Plasmids are self-replicating extra-chromosomal circular DNA molecules, distinct from the normal bacterial genome.
A DNA fragment containing the gene of interest is isolated from chromosomal DNA using restriction enzymes and then united with a plasmid that has been cut with the same restriction enzymes is then used to clone a gene. When the fragment of chromosomal DNA is joined with its cloning vector in the lab, it is called a recombinant DNA molecule. Following introduction into suitable host cells, the recombinant DNA can then be reproduced along with the host cell DNA.
Example of Recombinant DNA technology:
Figure 1: Cloning DNA in Plasmids.
By fragmenting DNA of any origin like human, animal or plant and inserting it in the DNA of rapidly reproducing foreign cells, billions of copies of a single gene or DNA segment can be produced in a very short time. DNA to be cloned is inserted into a plasmid (a small, self- replicating circular molecule of DNA) that is separate from chromosomal DNA. When the recombinant plasmid is introduced into bacteria, the newly inserted segment will be replicated along with the rest of the plasmid.
Reproductive cloning is a technology used to generate an animal that has the same nuclear DNA as another previously existing animal. Dolly is one of the examples that were created by reproductive cloning technology. In a process called "somatic cell nuclear transfer" (SCNT), genetic material from the nucleus of a donor adult cell is transferred to an egg whose nucleus (genetic materials) which has been removed. The reconstructed egg containing the DNA from a donor cell must be treated with chemicals or electric current in order to stimulate cell division. Once the cloned embryo reaches a suitable stage, it is transferred to the uterus of a female host where it continues to develop until birth. Reproductive cloning aims to produce offspring with similar genetic identity to previously existing organisms.
Dolly is created using nuclear transfer technology is not truly an identical clone of the donor animal. Only the clone chromosomal is the same as the donor. Some of the clone's genetic materials come from the mitochondria in the cytoplasm of the enucleated egg. Mitochondria are organelles that serve as power sources to the cell, contain their own short segments of DNA. Acquired mutations in mitochondrial DNA are believed to play a vital role in the aging process.
Dolly's success is proved that the genetic material from a specialized adult cell, such as an udder cell programmed to express only those genes needed by udder cells, could be reprogrammed to generate an entire new organism. Before this demonstration, scientists believed that once a cell became specialized as a liver, heart, udder, bone, or any other type of cell, the change was permanent and other unneeded genes in the cell would become inactive. That errors or incompleteness in the reprogramming process are believed the cause of the high rates of death, deformity, and disability observed among animal clones.
Example of Reproductive cloning:
Figure 2: Reproductive Cloning (Images from Time Magazine, March 10, 1997)
Therapeutic cloning is also called "embryo cloning," is the production of human embryos. The purpose of this process is not to create cloned human beings, but rather to harvest stem cells that can be used to study human development and to treat disease. Stem cells can be used to generate virtually any type of specialized cell in the human body. Therapeutic cloning aims to produce embryonic stem cells because of their multi-potentiality. It has been proposed as a source of cells for the replacement of damaged or defective tissue in adults. Using this form of cloning, cells are never allowed to develop into a complete organism.
Embryonic Stem Cells
When adult tissues are damaged, they are not able to repair themselves like neural system. The body is hardly or unable to repair the neurons in the spinal cord when the spinal cords are injured and the person will remain paralyzed for life. This is different to other tissues like the blood and skin, where the cells are lost and replaced frequently. Stem cells have the ability to become these mature or differentiated cells by undergoing differentiation. There are responsible for maintaining tissues at constant levels. Unfortunately, stem cells are normally difficult to find in adults. When they are isolated, they are often hard to grow into cell lines. It shows that adults are not likely to be a sufficient source of stem cells for therapeutic purposes. Embryonic stem cell lines have the potential to divide indefinitely and are pluripotent. An important consideration in therapeutic cloning is the possibility that the patient’s immune system will reject the transplanted cells. Each patient is an ideal donor for himself or herself because this eliminates the need to seek for a donor with compatible tissues. Cloning the individual to create unlimited stem cells would be an ideal way to circumvent this situation.
Figure 3: Somatic cell nuclear transferHere, a skin cell is removed from a patient. The nucleus of this cell is placed inside an enucleated oocyte and stimulated to divide. The resulting blastocyst can either be used to make embryonic stem cells, which are genetically identical to the donor, or they can be brought to term to create a genetically identical human being.
The source of these stem cells will become an issue if research with embryonic stem cells continues. Embryonic stem cells are taken from the early embryo, shortly after fertilization. At present, embryos that are frozen for couples undergoing in vitro fertilization are used to collect embryonic stem cells. Generally, due to the high failure rate of the procedure, multiple eggs are fertilized and stored. These are then transplanted into the mother one at a time until she becomes pregnant. They present a potential limited source of stem cells as long as the issue of tissue rejection is not addressed.
In the technique of somatic cell nuclear transfer (SCNT), it involves the removal of an egg from a hormonally treated female. The donor egg is enucleated and the nucleus of a somatic cell is transferred into its cytoplasm. The egg is then stimulated to start dividing. After sequential cell divisions, the blastocyst formed contains cells that will give rise to all tissues in the embryo. The blastocyst can be used to generate embryonic stem cells, which are genetically identical to the somatic cell donor, thereby eliminating the possibility of rejection when transplanted.
The cloning of Dolly brought to the forefront a longstanding debate about cloning human beings. Human cloning is a matter for the medical profession’s attention since it would involve medical procedures and technology, and it may result in the creation of new genetic and psychological conditions that would require professional care. Therefore, the medical profession must evaluate the ethics of human cloning.
How does human cloning work
The common method use to clone humans is somatic cell nuclear transfer (SCNT). This method was same as used to clone the famous Dolly the sheep. SCNT begins when doctors take the egg from a donor and remove the nucleus of the egg and creating an enucleated egg. A cell which contains DNA is taken from the person who is being cloned. The enucleated egg is then fused together with the cloning subject’s cell using electricity. This creates an embryo is implanted into a surrogate mother through in vitro fertilization (IVF). If the procedure is successful, then the surrogate mother will give birth to a baby that is a clone of the cloning subject at the end of a normal development period.
Example of human cloning:
Figure 4: somatic cell nuclear transfer in human cloning.
Existing Limits on Human Cloning
Based on the intrinsic limitations of human cloning technology, some mentioned undesirable applications of cloning are impossible which are prohibited by existing law, public policy, and professional ethical standards. In order to clarify the many mistaken beliefs about human cloning, public should be educated about the intrinsic technical limits of human cloning as well as the ethical and legal protections that should prevent abuses of human cloning.
Human clones would be identical in so far as they would have the same nuclear genes as the donor. However, in natural monozygotic twins which having identical genes does not result in two indistinguishable individuals. Although human cloning may be thought of as a sort of “delayed twinning,” twins may be more alike than clones since most twins are conceived and nurtured in the same environment in utero and often during childhood. Since environment has a profound influence on development, human clones likely would be different in terms of personality and other characteristics.
Several applications of human cloning are illogical because cloning would not produce exact replicas. In particular, human cloning would not be a solution to terminal illness or mortality. Children are already thought of as a way to “soften the blow of mortality” and clones may be seen as a more powerful approach since there is no sharing or mixing of genomes. But the clone would not be the same person as the cloned individual. The fact remains that the person does die and cannot be replaced.
There is some concern that human clones would be developed from cells obtained without one’s permission. Unlike traditional procreative methods, isolated somatic cells potentially could yield clones. If this technique becomes a possibility, the moral foundations of the therapeutic relationship would have to apply. These include trust, personal respect, and the healer’s fiduciary obligation to serve the patient’s health interests. Any attempt to clone a patient involuntarily would violate all three of these fundamental precepts of medical ethics.
Legal and ethical protections already stop the use of cloned children as discardable donor organisms. Medical ethics is grounded in the principle of nonmaleficence, or the avoidance of harm. Any involvement by a physician in the deliberate sacrifice or harm of children in order to harvest organs would violate this axiom. Further, this practice would be considered murder.
Advantages of Cloning
The full prospective of stem cells has not been fully explored, even until today. The issue of stem cells has led to arguments because embryos are generally used and they have to be destroyed and killed for the cells to be used. This is a serious issue in the side of religions and social morals. In spite of this, there are researchers who believed that stem cells can change the face of medicine in future. Knowing the fact that stem cells can be manipulated to mimic other types of cells, an advance in the cloning technology can provide new ways to treat incurable diseases like cancer Parkinson, Alzheimer’s heart attack, stroke and so on.
In addition, people who need organ transplants do not need to die of waiting anymore, because cloning gives hope to them. Normally, people requiring organ transplants to survive an illness often wait years for a suitable donor. However, these patients die waiting because there are long lists of people requiring organs. By means of cloning, die waiting scenes are not that significant anymore. It is because cloning can produce more animals that can act as suitable donors. For examples, pig livers have been successfully transplanted to human beings, as an interim measure until a human liver is found. For a more advance stage, if a scientist can clone the patient, then an identical liver can be produced, little or no repulsion will happens, and thus makes the operation safer and benefits the patient more. Additionally, cloning of these animals not put a burden on the world’s food supply.
Besides that, cloning can be used as a solution to infertility. Many infertile couples can’t be helped by vitro fertilization and the related techniques currently available. This offers couples dealing with infertility the chance to have a child of their own by inserting the cloned embryo into mother’s body. This point has become the advocate argue for cloning. In fact, although some states have already banned human cloning because of ethical issues, more couples struggling to have children are starting to consider the possibilities that cloning offer.
Moreover, cloning is being touted as a future answer to reverse the effects of aging. The anti-aging market is a major target because it is already a multibillion industry. Despite the best efforts of conservationists worldwide, some species are nearing extinction. The successful cloning of Dolly represents the first step in protecting endangered wildlife.
In agriculture industry, cloning could provide a means of cultivating plants that are stronger and more resistant to diseases, while producing more. The same could happen to livestock as well where diseases such as foot and mouth disease could be eliminated. Cloning could therefore effectively solve the world’s food problem and minimize or possible eradicate starvation.
Disadvantages of Cloning
The cloning of Dolly was seen as a success story, however, behind this success, many embryos were destroyed before the desired result was achieved. The process started with 277 eggs, and Dolly was the only single successful outcome. Without considering the success of cloning in other areas, the field of cloning still has a long way to go. Infertile couples, for example, could go through the same heartache and despair as they would if in vitro fertilization failed.
Furthermore, cloning is only the creation of a copy of the original one. A human clone would therefore only inherit the genetic traits of its predecessor. This includes the genes for abnormalities and diseases. Dolly the sheep is a good example of it. Dolly exhibited signs of what some suggested were premature aging, which are believed that the chromosomes of Dolly are inherited from the genetic materials of the old sheep, although this was firmly denied by her ‘developers’. Consequently, if a human cloned can survived, it does not guaranteed that it would develop normally.
Human can live on the Earth depend on the diversity of genes, that comes from parents having different sets of genes. Human cloning is just a copy of the original genes, which means it will decrease the diversity of genes. The most horrendous part of identical genes is that it will weaken our power and adaptations, make us subjected to great diseases easily. Another negative effect of cloning is inbreeding, as everyone has the same genotype and keep reproducing among themselves. This would lead us to our own extinction finally.
Religious Views on Human Cloning
Upon researching this topic, we findings that most written opinion are expressed by Christian writers. This is not to say that other religions are not speaking out. In fact, in, we would like to point out that all the religions we researched were against human cloning. The only exception to the rule that we could find was the religion of Islam. According to the book Clones and Clones: Facts and Fantasies about Human Cloning, states that: "Islamic scholar Abdulaziz Sachedina suggests that Islam could accept some therapeutic uses of human cloning ‘as long as the lineage of the child remains religiously unblemished’. The overwhelming majority, Christian, however, feel that we have no right to play the role of God, naming authority and stewardship from our heavenly Father as the reasons why. Buddhists even believe in the natural order of the world and to clone humans would be violating that rule. Chapter four of the text Improving Nature: The science and ethics of genetic engineering, it states that: "While Buddhism teaches that humans, unlike other creatures, have the opportunity to realize enlightenment, it does not teach that humanity is superior to the rest of the world."
Human cloning raises a variety of concerns, some realistic and others less so. It would be irresponsible to forge ahead with this new technology in the absence of serious discussion regarding the possible harms and benefits of cloning human beings. Until the benefits of human cloning are thought by society to outweigh the harms, it would be inappropriate for physicians to participate in human cloning.
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