- 1 Preimplantation genetic diagnosis
- 2 Genetic engineering of human gametes, zygotes, or embryos (aka germline modification)
- 3 Ethics of proposed germline modification of humans
- 4 See also
- 5 References
- 6 External links
Preimplantation genetic diagnosis
In medicine and (clinical) genetics pre-implantation genetic diagnosis (PGD or PIGD) (also known as embryo screening) is a procedure performed on embryos prior to implantation, sometimes even on oocytes prior to fertilization. The methods of PGD help to identify and locate genetic defects in early embryos that were conceived through in vitro fertilization (IVF). The IVF procedure is carried out by the removal of one or two cells when the embryo is at a specific stage in development. The PGD uses the IVF technique to obtain oocytes or embryos for evaluation of the organism's genome.
The PGD procedures allow scientist to identify damaged or mutated genes associated with diseases in the oocytes or embryos by using in-situ hybridization (ISH). The ISH technique labels specific nucleic acid sequences on a gene that can help detect genetic abnormalities.
Conversely, this technique can also help select for desirable traits by avoiding implanting embryos with genes that have serious diseases or disabilities. Examples of desirable traits that could be selected would be increased muscle mass, voice pitch, or high intelligence. Overall, the procedure of PGD to select for a positive trait is referred to the creation of a “designer baby”.
This is not a new technology - the first PGD babies, and thus also the first designer babies were created in 1989 and born in 1990.
A 2012 article by Carolyn Abraham in The Globe and Mail stated that "Recent breakthroughs have made it possible to scan every chromosome in a single embryonic cell, to test for genes involved in hundreds of 'conditions,' some of which are clearly life-threatening while others are less dramatic and less certain". There is already a "microchip that can test a remarkable 1,500 genetic traits at once, including heart disease, seasonal affective disorder, obesity, athletic ability, hair and eye colour, height, susceptibility to alcohol and nicotine addictions, lactose intolerance and one of several genes linked to intelligence. It is still difficult to get enough DNA for such extensive testing but the chip designer thinks this technical problem will be solved soon.
Regulation of Preimplantation Genetic Diagnosis
PGD has been used primarily for medical purposes, but as the possibilities of the procedure increase the idea of non-medical uses has become a popular topic of debate. Non-medical motivations could lead to potential problems when trying to make the distinction of when the procedure is needed or desired.
For example, PGD has the ability to select an embryo based on gender preferences (Stankovic). Since changing a gender is not needed, but desired this could cause much controversy. Additionally, the procedure is able to create a donor offspring or a “savior sibling”, which can assist a pre-existing offspring for medical purposes. The “savior sibling” is a brother or sister that is created to donate life-saving tissue to an existing child. There has been arguments against the procedures of “savior siblings” because many believe that this will lead humans closer to the creation of designer babies. For example one critque said, “the new technique is a dangerous first step towards allowing parents to use embryo testing to choose other characteristics of the baby, such as eye colour and sex”.
The artificial selection of traits through the use of PGD has become a widely debated topic and governments have started to regulate this procedure.
Many countries have already prohibited the complete procedure of PGD, these countries include Austria, Germany, Ireland, and Switzerland. While other countries have regulated PGD to only medical use, these countries include Belgium, France, Greece, Holland, Italy, Norway, and the United Kingdom.
In contrast, the United States federal law does not have any regulation of PGD. Those who are in favor of PGD believe the government should not be involved in the procedure and parents should have a reproductive choice. The opposing side has argued that PGD will allow embryo selection based on trivial traits. While other critics believe that this procedure could lead to a new form of Eugenics.
The regulation of PGD has become an important topic, however much of the artificial trait selection remains only prospective until technology advances. For example, scientist do not know which specific gene is associated with specific traits, like voice pitch or intelligence. Nevertheless, with the current rate of technological advancements, it is believed that in the next twenty years the artificial selection of desirable traits will exist.
Genetic engineering of human gametes, zygotes, or embryos (aka germline modification)
The other use for designer babies concerns possible uses of gene therapy techniques to create desired traits of a child, such as disease resistance, sex, hair color and other cosmetic traits, athletic ability, and intelligence.
Understanding of genetics for human traits
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Genetics explains the process of parents passing down certain genes to their children. Genes are inherited from both biological parents, and each gene expresses a specific trait. The traits expressed by genes can be something physically seen—such as hair color, eye color, or height—or can be things such as diseases and disorders.
Human genes are found within chromosomes. Humans have 23 pairs of chromosomes, 43 individual chromosomes. 23 chromosomes are inherited from the father, and 23 from the mother. Each chromosome can carry about 20,000 genes.
Researchers have already connected the genes in the striped zebra fish which control the colour of the fish to genes in humans that determine skin colour. Many other things could be discovered in further years especially with the new possibilities of cloning animals.
Scientists have been able to better understand the genetic traits for human through projects such as The Human Genome Project. This project was launched around 1990 and was an international research project that had an end goal of mapping and understanding every gene in the human body. As a part of the Human Genome Project, we have been able to pin point specific locations for about 12,800 specific genes within different chromosomes.
Germline modification has been around since the 1980’s, as there have been successful animal trials dating back to that time. In order for germline modification to be successful, medical professionals must know how to introduce a gene into the patient's’ cell and the germline so that it will be transferred subsequent generations and still maintain the proper functionality. The way in which genes are integrated into the DNA is what determines that difference between germline modification and somatic cell modification. In order to be transferred to subsequent generations, these changes need to be carried out through the development of germ cells. Changes in the germline result in permanent and heritable changes to the DNA. While amplification of positive effects would occur, there is also the risk that amplification of possible negative effects would also occur. Since the results are generational, it is more complicated to study the long-term effects and therefore it is not a simple task to figure out if the benefits of germline modification outweigh the harm. Allowing families to have the ability to design their children and select for desirable traits is another major concern that germline modification presents.
Germline modification can be accomplished through different techniques that focus on modification of the germinal epithelium[disambiguation needed], germ cells, or the fertilized egg. Most of the techniques include transporting transgenes and then the transgenes are integrated with the DNA of the zygote. After integration, the transgene becomes a stable and functioning portion of the host’s genome. One technique involves a specific sequence of cloned DNA being inserted into the fertilized egg using the microinjection technique. The sequence in inserted directly into the pronucleus. The second technique uses the transfection process. Stem cells obtained from the embryo during the blastocysts stage are modified, combined with naked DNA, and the resulting cell is reinserted into the embryo that is developing. The third technique focuses on carrying DNA into the embryo by using retroviruses.
Feasibility of gene therapy
Gene therapy is the use of DNA as a pharmaceutical agent to treat disease. Gene therapy was first conceptualized in 1972, with the authors urging caution before commencing gene therapy studies in humans. The first FDA-approved gene therapy experiment in the United States occurred in 1990, on a four-year-old girl named, Ashanti DeSilva, she was treated for ADA-SCID. This is a disease that had left her defenseless against infections spreading throughout her body. Dr. W French Anderson was a major lead on this clinical trial, he worked for the National Heart, Lung, and Blood Institute Since then, over 1,700 clinical trials have been conducted using a number of techniques for gene therapy.
Techniques in Gene Therapy
The techniques used in gene therapy, which is also referred to as vectors, have a method of using a healthy gene to attack and replace an infected gene. The amount of techniques or vectors that have been used to conduct these clinical trials vary. A few of the techniques are basic processing, gene doping, and viral vectors. Viral infections can be life threatening in patients who are immune-compromised because they cannot mount an effective immune response. Approaches to protection from infection using gene therapy include T cell-based immunotherapy, stem-cell based therapy, genetic vaccines, and other approaches to genetic blockade of infection. There are also other approaches known as, T Cell-Based Approaches, Cell Therapy, Stem-Cell-Based Approaches, and Genetic Vaccines.
Basic processing can be achieved through replacement of a mutated gene, inactivation of a mutated gene, or introduction of a new gene to help fight a disease caused by mutation. Secondly, gene doping is a procedure of gene therapy modulates gene expression of a particular gene. This procedure is mainly used to improve athletic ability for sporting events. This is a genetic form of human enhancement that is able to treat muscle-wasting disorders. It is a highly controversial procedure because the results do nothing unusual to the bloodstream, so athletic officials would be unable to detect chemicals in a blood or urine test. An example of gene doping would be proving athlete with erythropoietin (EPO) with is a hormone that increases the red blood cell count. Lastly, viral vectors are able to mimic the methods of a normal virus in the human body to introduce ‘good’ genes into a human cell. For instance, scientists are able to positively change the host’s genome by removing the genes that cause disease from a virus and replacing it with genes of the desired trait (“Types of Gene Therapy”).
The techniques above have been used by scientist, but the most popularized techniques are Naked DNA and DNA complexes. The injection of the Naked DNA is the simplest method of the vector delivery method. The Naked DNA is a histone-free, modified DNA sequence that removes proteins that would normally surround it. This form of delivery is sometimes used as a natural compound, but the United States has been making large waves of synthetic compounds for gene delivery. The other form, which is DNA Complexes, has been used when a compound is crossed with a chemical mix in order to produce the desired compound. There are other studies that are currently underway that have have been referred to as the hybrid method because there is a combination of two or more gene therapy techniques used. This can instill the idea that the desired gene will stick during the delivery, transfer, and implant.
The manipulation of an organism’s genome for a desirable trait is related to the medical procedure of cloning. The process of cloning results in making genetically identical organisms. Moreover, scientists can use gene therapy vectors to modify the DNA to be identical to a particular organism. Moreover, the techniques established by the field of gene therapy can potentially be used to create “designer babies”. This can be achieved through the use of IVF to assist in creating a genetically designed baby.
Disease Control in Gene Therapy
Gene therapy is being studied for the treatment of a wide variety of acquired and inherited disorders. Retroviruses, adenoviruses, poxviruses, adenoviruses poxviruses, herpesviruses, and others are being engineered to serve as gene therapy vectors and are being administered to patients in a clinical setting. Some of the other genetic disorders that can be tried in a clinical trial are ADA-SCID, which as stated earlier, is Severe Combined Immune Deficiency, CGD which is Chronic Granulomatous Disorder, and Hemophilia. These examples of disorders are only a few among a numerous amount of others that are being discovered. Some of the acquired diseases that can be potentially controlled in a clinical trial with gene therapy are cancer and neurodegenerative diseases such as Parkinson’s Disease or Huntington's Disease.
Ethics of proposed germline modification of humans
Lee Silver has projected a dystopia in which a race of superior humans look down on those without genetic enhancements, though others have counseled against accepting this vision of the future. It has also been suggested that if designer babies were created through genetic engineering, that this could have deleterious effects on the human gene pool. Some futurists claim that it would put the human species on a path to participant evolution. It has also been argued that designer babies may have an important role as counter-acting an argued dysgenic trend.
There are risks associated with genetic modifications to any organism. When focusing on the ethics behind this treatment, medical professionals and clinical ethicists take many factors into consideration. They look at whether or not the goal and outcome of the treatment are supposed to impact an individual and their family lineage or a group of people. The main ethical issue with pure germline modification is that these types of treatments will produce a change that can be passed down to future generations and therefore any error, known or unknown, will also be passed down and will affect the offspring. New diseases may be introduced accidentally.
The use of germline modification is justified when it is used to correct genetic problems that can’t be treated with somatic cell therapy, stabilize DNA in a mating that has the potential to be high risk, provide an alternative to the abortion of embryos that genetically problematic for a family, and intensify the incidence of genes that are favorable and desirable. This can ultimately lead to perfected lineages on a genotypic level and possibly a phenotypic level. Ultimately, these issues raise potential questions about the welfare and identity of individuals that have been genetically modified through the germline.
Safety is a major concern when it comes to the gene editing and mitochondrial transfer. Since the effects of germline modification can be passed down to multiple generations, experimentation of this treatment brings forth many questions and concerns about the ethics of completing this research. If a patient has undergone germline modification treatment, the coming generations, one or two after the initial treatment, will be used as trials to see if the changes in the germline have been successful. This extended waiting time could possess harmful implications since the effect of the treatment is not known until it has been passed down to a few generations. Problems with the gene editing may not appear until after the child with edited genes is born. If the patient assumes the risk alone, consent may be given for the treatment, but it is less justified when it comes to giving consent for future generations. On a larger scale, germline modification has the potential to impact the gene pool of the entire human race in a negative or positive way. Germline modification is considered a more ethically and morally acceptable treatment when a patient is a carrier for a harmful trait and is treated to improve the genotype and safety of the future generations. When the treatment is used for this purpose, it can fill the gaps that other technologies may not be able to accomplish.
Since experimentation of the germline occurs directly on embryos, there is a major ethical deliberation on experimenting with fertilized eggs and embryos and killing the flawed ones. The embryo cannot give consent and some of the treatments have long-lasting and harmful implications. In many countries, editing embryos and germline modification for reproductive use is illegal. Currently, the United States of America restricts the use of germline modification and the procedure is under heavy regulation by the FDA and NIH. Germline modification would be more practical if sampling methods were less destructive and used the polar bodies rather than embryos.
- Human enhancement
- Human genetic engineering
- Eugenics in the United States
- Genetically modified organism
- Germinal choice technology
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