The development of genetic technology in Biology over the last decades has enabled the practice of theorized cloning techniques. In this essay, therapeutic, embryonic, and reproductive cloning have been studied in detail and summarized. The objective of the paper is to differentiate therapeutic, embryonic, and reproductive cloning, their various advantages and disadvantages, as well as challenges experienced in their practical development and how they are applied in various fields of research, medicine, and agriculture. The research also seek to understand ethical issues surrounding the three types of cloning.
Therapeutic, Reproductive, and Embryonic Cloning
Cloning is the science of producing genetically identical multiple copies, also referred to as clones, of DNA fragments, cells, group of cells, organ or the whole organism. Naturally, cloning occurs through the procedure of abiogenic/asexual reproduction whereby life forms, such as, microscopic organisms, parasites, and plants deliver offspring’s that are genetically indistinguishable from their parents. However, due to advancement in technology and research, artificial cloning has become possible. Artificial methods of cloning include therapeutic, reproductive, and embryonic cloning (Sourbeer, Wisnecki, Palomar College, & Insight Media, 2008).
Modern genetic technology has enabled man to produce clones from existing individuals. For example, therapeutic cloning is used to produce stem cells which can be coerced to develop into a specific organ for organ transplant. Reproductive cloning has helped to produce whole organisms, which is an important breakthrough as it helps in restoring endangered species. Artificial cloning has raised various ethical issues, especially on human cloning, supporters contend in the sense that cloning for medical purposes should be developed to help create organs for organ transplant to patient who lack compatible donors. It also minimizes the need to use immunosuppressive medication which can have severe effects on patients. They also argue that reproductive cloning may help parents who cannot procreate. Religious groups are highly opposed to cloning as it opposes the will of God. Other opponents argue that the cloning technology is not developed enough to be of safe use as it is prone to abuse
The perspectives of human cloning are largely theoretical as human therapeutic and reproductive cloning are not in commercial use yet (Andrews, 1999). However, animals and plants are largely cloned in laboratories and in livestock production for study. To control and secure the cloning technology, ethical guidelines have been established by international communities through the Universal Enormous Declaration on the Human Genome and Human Rights.
Therapeutic cloning is also referred to as somatic cell transfer. The nucleus of a cell is inserted into a fertilized egg whose nucleus has already been removed. The nucleated egg divides sequentially to form blastocyst. The blastocyst contains undifferentiated pluripotent cells known as stem cells. Stems cells are extracted and used to grow cells that match those of the patient. The cells are then transplanted into the patient for treatment. The stems cells can also be coerced to grow into an organ of interest for organ transplant to the patient, whereby the organ is a perfect match. Consequently, immunosuppressive drugs are not used whereas organ rejection is low (Gottweis, Salter, & Waldby, 2009).
After being transferred to the enucleated egg, the nucleus is reprogrammed to the environment of the egg. Hence, genes that were dormant (turned off) are reactivated. For an inadequately comprehended process, re-programming includes sensational changes in the patterns of genes which are dynamic in the nucleus. Instead of the grown-up genes making the egg to carry on like a grown-up cell, the egg makes the nucleus go in backwards along a separation succession, bringing about an embryonic type of cell. Because of somatic/therapeutic cloning, the already unfertilized inherits the properties of a fertilized egg and commence with the initial stage of development into an embryo (Gottweis, Salter, & Waldby, 2009).
Research cloning is widely used to develop and culture stem cells from undeveloped embryos for research purposes. This helps in understanding human development, as well as in studying the aspects of various disorders. This may help to come up with potential treatment of various diseases such as Alzheimer’s and diabetes. Therapeutic cloning helps to restore, regenerate, and develop tissues and organs for explicit burns and injuries. Moreover, it is crucial for spinal injuries, as well as for organ transplant in the treatment of cerebrovascular conditions, treatment of monogenic and degenerative diseases, as well as treatment of Parkinson’s disease (Cloning & transgenes, 2012).
The convenience of somatic cloning lies in the aspect that somatic cells can easily been acquired and cultured in the laboratory. After obtaining somatic cells, scientists can either add or delete specific genes of the animal under research in accordance with the scientist point of interest. However, stresses placed on oocyte and the introduced nucleus of the donor pose adverse effects on the success of the cloning. A significant number of cell loss in the early stages of development is exhibited due to these stresses. This is highly evident in the research where dolly was created, whereby 277 eggs were used in the process which created only 20 viable embryos. Three embryos survived to maturity for birth and only one lived to adulthood.
Therapeutic cloning does not always lead to all of the donor’s genetic transfer as mitochondrial DNA is left behind. Only the mitochondrial DNA of the oocyte is inherited by the offspring. It is also difficult to get enough cells. It is, therefore, important to grow them in vitro. During cloning, there is also the possibility of the formation of tumor cells due to the rigorous process involved. Therapeutic cloning differs with reproductive cloning whereby in the former, the blastocyst stem cells are harvested and are allowed to grow in cultures to develop specific cells, tissues, and organs of interest. The embryo is not implanted in a surrogate mother, unlike in reproductive cloning whereby the developing embryo is implanted to a carrier mother and the normal process of growth and development is allowed till adulthood.
Scientist have observed that the nucleus of cells with close proximity to reaching death have the ability to change their lifespan. This may have adverse effects on cells, tissues and organs if transplanted in the specific animals.
However, therapeutic cloning may have great advantages in conserving life and in treatment of various disorders which may not have been treated by medical means. It is also important to people who show serious negative effects if immunosuppressive are used on them. This would also prevent people undergoing organ transplants from opportunist infections caused by use of immunosuppressive drugs. Therapeutic cloning also gives scientist a chance to modify the cells to be transplanted by either carrying out gene editing or adding genes according to their specific interest. For this reason it has served a great deal in large scale production of insulin for commercial use thus helping persons with diabetes (Gottweis, Salter, & Waldby, 2009).
In this type of cloning, somatic cell’s nucleus are inserted in an oocyte whose nucleus has been removed. The egg containing the implanted nucleus is stimulated to begin the process of cell division, which leads to the formation of a blastocyst. The blastocyst/preimplantation embryo is implanted in the uterus of the animal to begin the normal period of growth resulting to further development of the embryo.
The offspring resulting from this has identical DNA as that of the donor. However, not all genetic material is inherited from the donor as the mitochondrial DNA from the donor is not transferred to the clone (Klotzko, 2006). Reproductive cloning differs with therapeutic cloning in that, in reproductive cloning, the cloned embryo is present to develop to maturity and later to adulthood, for example, in Dolly the sheep born on 5th July 1996, unlike in therapeutic cloning whereby embryos are destroyed in the process of harvesting stem cells to grow various organs.
It is possible to make a genetic modification to the embryo either by addition of desired genomes or deletion of undesired genes to be expressed in the clone. Through reproductive cloning, infertile couples can be able to have a genetically identical child to one of them. Reproductive cloning has had great beneficial effects on livestock farming, as it helps to replicate desired combinations of expressions in animals such as efficient and sustained growth rate, high milk production, and high meat production without mixing of genetic traits as that which occurs when animals reproduce sexually. This has greatly impacted the agricultural field positively as it has helped in sustainable production of agricultural commodities.
The knowledge on reproductive cloning can be used in restoring endangered species and conserving certain gene pools. If used only for medical purposes on humans, reproductive cloning can play a great part in studying various genetically disorders, understanding human development, organ transplant, and in healing certain diseases
Factors involved in DNA chromatin, imprinting or alteration of the chromosome influence the outcome of the gene expression in the clone (Gottweis, Salter, & Waldby, 2009). Since method requires the in vitro generation and formation of an embryo, prohibitive therapeutic cloning can result to serious in hindering essential medical research based on therapeutic cloning. Other limiting factors to reproductive cloning include epigamic methylation of genes, alteration, and changes in the structure of chromosomes.
Identical twins are an example of a natural embryonic cloning. Modern advancement in genetic technology has made it possible to create artificial copies of a fertilized egg. Scientists have managed to culture successfully embryonic stem cells from pre-implantation embryos. In this type of cloning, fertilization of the egg is done in vitro. The fertilized egg undergoes cell division sequentially. At this stage of development, the cells are separated and each is allowed to divide, develop, and grow into separate but identical blastocysts. Thus, the embryo are monozygous but diploid in nature like the ones formed naturally. They have a complete match of DNA. Embryonic cloning can also be done to eggs containing donor nucleus DNA soon after the process of cell division has occurred. The core reason of performing embryonic cloning is to obtain 100% identical offspring.
Embryonic cloning has high potentiality in the field of research. Scientists argue that embryo cloning can lead to great breakthroughs in the field of stem cell research including the production of cells, tissues, and organ types.
Theoretically, the cells, tissues, and organs can be used for transplants and medical therapy. In agriculture, embryonic cloning has great advantages indicating potential in increasing production in animals and plants by maintaining those with desirable traits thus increasing food security (Royal Society (Great Britain), 2000).
However, although embryonic stem cells have the greatest differentiation capacity, the use of these cells for therapeutic medication is faced with many challenges. The unmanageable division and development of these cells in a syngeneic transplantation can cause development of abnormalities. This uncontrollable division often leads to formation of cancerous body tumors on the specific organ of concern. Thus, scientists are faced with challenges of differentiating the stems cells to develop into viable cells consistently. For example, embryonic undifferentiated cells can form cancerous tumors after transfer into histo-compatible animals. It is of importance that a suitable state of differentiation before transplant is established. The appropriate separation states for distinctive types of cells have not yet been built. Moreover, identifying and focusing on those undifferentiated units to their proper organ parts may also pose to be a challenge.
Cloning has raised various ethical issues, especially on matters concerning human cloning. Religious groups are highly opposed to cloning as they argue that cloning differs with God’s purpose for procreation. Destruction of embryos leads to destruction of life. Other opponents argue that cloning in humans, plants, and animals if not used appropriately can lead to abuse of the technology as some may use it for selfish gain by modifying various organisms to suit their specific interest. Although cloning raises various ethical issues, it is of importance when used to save and conserve life and more so when used responsibly. Although therapeutic, embryonic, and reproductive cloning promises a future full of possibilities, there are many challenges to overcome before therapeutic, embryonic, and reproductive cloning are used on humans. International communities should put into place strict guidelines to be adhered on matters involving cloning in order to keep cloning on check.
Andrews, L. B. (1999). The clone age: Adventures in the new world of reproductive technology.
New York: Henry Holt.
Gottweis, H., Salter, B., & Waldby, C. (2009). The global politics of human embryonic stem cell
science: Regenerative medicine in transition. Basingstoke [England: Palgrave Macmillan.
Klotzko, A. J. (2006). A clone of your own? The science and ethics of cloning. New York:
Cambridge University Press.
Royal Society (Great Britain). (2000). Therapeutic cloning. Royal Society.
Sourbeer, D., Wisnecki, B., Palomar College., & Insight Media (Firm). (2008). Genetic
technology. New York: Insight Media.
Sourbeer, Wisnecki, Palomar College, & Insight Media.