Part 1: Creative Conception – an examination of some assisted reproductive technologies
Question 1:
a) What does ‘preimplantation genetic diagnosis’ mean?
Preimplantation genetic diagnosis (PGD) is a prenatal genetic profiling procedure that is commonly used prior to implantation to assist in identifying genetic defects within embryos. It involves the testing of a few biopsied cells from oocytes or embryos generated in vitro. PGD was first performed in 1990 and has now an established and expanding range of applications with continual technical progress. The diagnosis aims to determine if the embryo carries a known genetic abnormality that is reflected in one or both of the genetic parents. Through this diagnosis, preventative measures are often used in order to avoid certain genetic diseases and disorders from being carried on to within the genes of the child. Consequently, PGD is only one of few present options to avoid a high risk of having a child affected with a genetic disease prior to implantation and thus a preventative measure to avoid heritable genetic diseases and possible pregnancy termination.
b) Explain why PGD needs to be used in conjunction with IVF technology?
A preimplantation genetic diagnosis (PGD) is required in conjunction with the use of Invitro fertilization (IVF) technology in order reduce the risk of passing on inherited genetic conditions such as cystic fibrosis or sickle cell anemia which are specific single-gene conditions that structurally change a parent’s chromosomes. Consequently, the use of PGD in conjunction with IVF has dramatically improved the chance of a successful IVF pregnancy where prior IVF failures have existed for the couple. Single cycle IVF success rates (the change of becoming pregnant) following PGD are raised significantly as the PGD determines that the 2 or 3 embryos that are known to be chromosomally normal are transferred.
Question 2:
Describe the twofold benefits (advantages) to the family that result from PGD application.
As reflected previously, the application of PGD has higher success rates during the IVF process and reduces the risk of passing on inherited genetic conditions to the children. By only transferring and presenting ‘healthy’ embryos with no visible abnormalities such as an unusual number of chromosomes will lead to the birth of a healthy child. As well as this, it avoids the transfer of embryos that are ineffectively unable to be implanted or lead to pregnancy loss (miscarriage). Thus, couples who have applied PGD whilst creating a family have seen a significant increase in obtaining a healthy pregnancy. These success rates also highlight the lower amounts of transfers required to become pregnant as through the use of PGD with a single embryo transfer sees a 58% ongoing pregnancy rate.
Question 3:
Debate surrounding embryo screening continues in Australia and around the world. Write a list of social issues that arise from the application of this technology. Consider social implications such as; relationships, economic, legal and ethical concerns.
Despite its advantages for increasing the likelihood of providing couples with a healthy pregnancy and child; several social issues are paramount within our society regarding the use of PGD. This is as a result of the ethical and moral implications in can place upon individuals and their community. These concerns are:
- Embryos are created that the couple never intends to use and there is low chances that these embryos with an unwanted mutation will be ‘adopted’. Consequently, individuals who uphold the notion that think human life is from fertilisation onward may share the moral obligation that PGD and abortion are alike in this circumstance.
- Alongside these views, a legal implication is developed in which Australian judicial decisions may regard the use of PGD and alas the disuse of embryo’s can be posed as an illegal termination of the child.
- Selective implantation prevents certain genotypes from coming into existence and accordingly the procedure is discriminatory to individuals with disabilities and threatens genetic diversity.
- Moreover, by allowing selection of the genes of the child, possible implications to the parent-child relationship occur; where it deprives the parent and child from the opportunity of making most with what ‘nature’ provided them with.
- This technique can also allow a selection of the sex of the embryo and in the future may allow for the selection of other non-health related traits. These realistically potential applications threaten further ethical liabilities where possible children are selected based upon their gender and other desirable traits.
- PGD is an expensive procedure and despite being openly available it limits its markets who can afford the technologies and consequently discriminates against lower socioeconomic couples and families.
Question 4:
Consider carefully the positions of people (on different sides of the PGD debate. Identify at least two different stakeholders (one for and one against) and prepare arguments that highlight their points of view (show reasoning).
As a result of the social and moral implications that have arisen for PGD, stakeholders in the completion of the procedure take opposing perspectives. Whilst, medical companies have significant financial gain from these procedures, advocates for minority groups such as the disabled community expose the inherent discrimination and allowing the selection of embryos without heritable genetic mutations.
Advocates for those with disabilities oppose PGD for similar ethical reasons for opposing germline gene therapy and genetic engineering. These stakeholders reflect that selective implantation in order to avoid certain genotypic mutations discriminates against those with disabilities and consequently threatens genetic diversity. Spokespersons for the disabled community have claimed that expensive and unnatural procedures for selecting against embryos with serious genetic mutations epitomises an immoral notion that individuals with disabilities are inferior to those without.
However, fertility treatment companies and genetic counsellors often acknowledge, yet, contend this concept as they expose the possible psychological impact of possessing a disability. Consequently, they justify that providing reproductive freedom for couples that desire to reduce their risk of having a child with a disability remains morally acceptable. Further, these stakeholders reflect that PGD allows for an improvement of quality of life for the family through avoiding disabilities that are financially, emotionally, mentally and physically exhaustive. Yet, the prejudicial perspective of the fertility medical workforce places an imbalance upon these arguments, as they have financial benefits from couples who commit to the procedure.
Question 5:
Other examples of assisted reproductive technologies include artificial insemination and artificial pollination. Create a table that compares the processes and outcomes of these TWO technologies. Give an example where each is used in agriculture.
Artificial Insemination Artificial Pollination
Summary Process Sperm is collected from the chosen male and artificially introduces the sperm into several selected females. The process became commercially widespread in the 1980s due to further research and discovery of effective storage and transportation of sperm.
The sperm is removed using a mechanical stimulation or an artificial vagina. It is then divided and stored in straws that are then frozen in liquid nitrogen for storage.
The semen is then transferred to the female in a sterile artificial insemination gun that is inserted into the vagina to the cervix where the semen is then placed. Stamens of a flower are removed and the stigma of the same flower is then dusted with pollen to allow it to self-pollinate. This provides the breeder with more control over the breeding process.
Records indicate that artificial pollination was used in ancient eras where Assyrian carvings date the process to 870 BCE.
Advantages
- Sperm transport is more cost effective and provides a reduction of danger for the animal rather than transporting large animals’ long distances.
- A male can produce offspring beyond the years of their death.
- Possible future use to increase numbers of endangered species as reflected through attempts of artificial insemination of grey nurse sharks and gorillas.
- Primary method for assisted reproductive technology for cattle, sheep, pigs and performance horses. Enables production of offspring with favourable characteristics, (e.g. disease resistant fruit).
- Ensures a greater yield of crop and seeds.
- Creation of new varieties of plants.
Disadvantages
- Costly, due to specialised equipment.
- Time consuming
- Potential to injure the female.
- Reduction in genetic diversity
- Possible unsustainability for its environment or further reproductive success.
- Overuse can lead to crops that are to similar and consequently create a reduction in biodiversity.
- Increased susceptibility to disease.
- Lower fruit and seed germination rates than natural insect-pollination.
Use in agriculture Artificial Insemination in Beef Cattle
Cattle breeders often choose to use artificial insemination in their herds to gain:
- Genetic Improvement
- International genetic access
- Reduction in the amount of bulls needed.
- Join a bull with more females than they could naturally in the mating season.
- Reduce risk of infection from venereal diseases. Artificial Pollination in Maize (Corn)
Artificial pollination in maize has produced a hybrid that has:
- Increased Growth Rate
- Greater Uniformity
- Increased Yield.
Hybridisation such as in corn introduces new combinations of alleles that are fertile.
Part 2: Crispr – a new frontier in genome editing
1. What exactly is CRISPR and how does it work?
‘CRISPR’ which stands for ‘clusters of regularly interspaced short palindromic repeats’, palindromic meaning that it reads the same both forwards and backwards that is a special kind of DNA found in bacteria. It is a specialised region of DNA that has obtained two distinctive features of nucleotide repeats and spacers. The repeated sequences of nucleotides are distributed throughout the CRISPR region whilst the spaces are DNA interspaced among these repeated sequences.
The spacers are taken from viruses that previously attacked the organism and serve as a ‘memory bank’ to fight off future ‘attacks’. After a spacer is incorporated and the virus attack’s again then a segment of the CRISPR is transcribed and processed into CRISPR RNA ‘crRNA’. The nucleotide sequence then is used as a template to produce complementary sequence of single-stranded RNA.
When used in association with Cas9 protein which is an enzyme that is an enzyme that cuts foreign DNA, scientists can edit DNA sequences within living cells. Cas9 binds to crRNA and tracrRNA (trans-activating RNA) that guide Cas9 to the target site where it will make the cut of DNA. The Cas9 cuts both strands of the DNA double helix to make a ‘double stranded break’ whilst short DNA sequences known as PAMs (protospacer adjacent motifs) are used as a safety mechanism to ensure the Cas9 makes the cut in the right area.
Consequently, CRISPR-Cas9 technology can allow researchers and scientists to alter DNA sequences and ultimately permanently alter gene functions. This technology thus has the capability and potential to be applied in correcting various genetic defects, treatment of disease and improving crops; with a simple programmable genome editing tool. Cas9 can be directed with this tool to cut any region of the DNA and once the DNA is cut, the cell’s natural repair mechanisms begin to work to introduce mutations or other changes to the genome as desired. The technology is easy to use and four times more efficient than previous gene editing tools such as ‘TALENS’.
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