Assisted Reproductive Technology Report
Inherited genetic disorders is a reason couples plan to not conceive children nowadays. There are many parents who are reluctant to conceive children due to the fact that: one or more parent could have an inherited genetic abnormality, parents could already have a child with a genetic disorder, one/more parents have a history of genetic disease, a parent has a chromosomal abnormality or a couple has gone through a pregnancy loss as a result of a genetic disease.
Each body is required to have 23 pairs of chromosomes (46 in total), which hold about a total of 20,000 to 25,000 genes. One pair is given by one parent. “Chromosomes are the structures that hold genes. Genes are the individual instructions that tell our bodies how to develop and function; they govern physical and medical characteristics, such as hair colour, blood type and susceptibility to disease” ("Chromosome Abnormalities"). Inherited genetic disorders can be split into two common areas: single gene inheritance and chromosomal abnormalities.
“Single gene disorder is caused by variations (or mutations) in the DNA sequence of a specific gene” ("Single Gene Disorders"). The DNA is changed during this disorder, which negatively impacts the gene codes (mostly protein), causing them to be changed or missing. Parents are afraid to have children with this disorder as some don’t survive after birth or get really sick. Passing on a genetic disorder is dependent on the characteristics of the disease, including inheritance pattern. Single gene disorders are caused by specific gene variations, thus it tends to run in families ("Single Gene Disorders"). There are different types of single gene disorders: autosomal dominant, autosomal recessive, x-linked recessive and x-linked dominant. Autosomal dominant is when there is one pair of a changed gene from one parent. Fig. 1 showcases an example of an inheritance pattern for a dominant disease. Autosomal recessive are when two pairs of changed genes are transmitted from both parents. X-linked recessive is when there is gene alteration on the X chromosome and common amongst males (women have another copy of an X chromosome). X-linked dominant is similar to autosomal dominant inheritance and common amongst females, however is rare. Common examples of single gene disorder is cystic fibrosis, fragile X syndrome, Huntington disease or muscular dystrophy ("Single Gene Disorders | Genetics Overview | A Look Inside Thrombotic Storm At Miller School Of Medicine").
Fig. 1
Chromosomal abnormalities are when there is a change in the number or structure of chromosomes. This normally occurs during the development of the embryo or inherited from a parent. There are two types: numerical abnormalities and structural abnormalities. Numerical abnormalities are the loss or gain of chromosomes. Structural abnormalities are when sections of DNA are lost or gained by a chromosome. Fig. 2 shows the common ways that the abnormalities occur. Examples are down’s syndrome and Edward’s syndrome ("What Is A Chromosome Disorder?").
Fig. 2
A solution to inherited genetic disorder is to use preimplantation genetic diagnosis (PGD), which is a part of assisted reproductive technology (ART). This solution is used to reduce the risk of transmitting a genetic disease to an offspring. “It is a procedure used prior to implantation to help identify genetic defects within embryos” ("Preimplantation Genetic Diagnosis: Benefits & Concerns"). PGD is done during in-vitro fertilisation (IVF), where “fertilisation, embryo development and implantation is done to get a woman pregnant” ("What Is In-Vitro-Fertilization (IVF)?"). The following steps are done for PGD: the embryos are generated by IVF or ICSI, then from an embryo, cells are removed micro surgically for genetic testing. The DNA in the embryos are assessed for any genetic disease. Those with no genetic condition are used for implantation in the woman’s uterus. Fig. 3 shows this process. This is mainly for couples who have a history of genetic disease, are carriers of gene disorders/chromosomal abnormalities, women who had miscarriages, women with IVF failures or women aged 35 and over. Fig. 4 below shows the reasons people undertake PGD, some couples take it after a preimplantation genetic screening (PGS) of the embryos, it only looks for aneuploidy (abnormal numbers of chromosomes). PGD can allow parents to have the choice of choosing the healthy embryos to be implanted in the uterus. It gives a chance for parents to live without the risk of their child being affected by gene disorders. The price for PGD varies across countries, but is within $5000 to $12000 ("PGD Testing – Procedure Cost, Risks & Benefits | Infertility Aide".).
Fig. 3
Fig. 4
This solution is effective, as it has had success on many patients. According to the Fertility Institutes (based in the United States, Mexico and India), their IVF success rates have increased when the embryos were known to be chromosomal normal. This procedure is feasible, since it is allowed in many countries. This can be seen in the table below (Fig. 5). Countries which are not allowed to conduct PGD are those where the Catholic Church has denied it. The advantages of using this technique is that it can test for about 100 genetic conditions, which take into account any possible genetic conditions. Couples who would have not considered to conceive children due to genetic disease and also reduces the risk of having children with the same problem. Women who use PGD have a low risk of having a miscarriage. Disadvantages of PGD include the uncertainty of conceiving a child with a genetic disease, PGD can’t completely eliminate the risk of having a child without it. IVF, which is required for PGD, has its risks, such as ovarian hyper stimulation syndrome and an increase risk of birth defects. The cost of PGD is very high, and is usually not covered by medical insurance. Some parents also use PGD for gender selection, which is considered unethical in many countries ("PGD Benefits & Risks | Denver | Colorado Fertility Specialists").
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Fig. 5
Discarding embryos is a common practice during PGD. PGD has multiple reasons for discarding the embryos. The ethical implications of PGD are evaluated in three different areas: destroying embryos, gender selection and eugenics.
For each successful embryo plantation, many embryos are discarded, as they are not suitable (they have a genetic disorder). An example of the usage is when out of 29 embryos screened, only 6 were suitable. Out of the 6, only 1 baby was created (). Some people raised the question, if 29 lives should be discarded/destroyed just to avoid the chance of genetic disease. People find this an unethical practice as it kills potential babies. ….. However, these discarded embryos are now being used in embryonic stem cell research. Stem cells are allowing the…..
Some couples discard embryos based on gender selection. This could result in a gender imbalance. If parents are able to choose the gender of the baby, such as in Asian countries, they would prefer male offspring (they are deemed to be more ‘superior’). In the United States, about 55% of couples would opt to continue with the procedure if the gender is not desirable. That is a fairly low amount, which shows that there is a possibility where the difference in the sex ratio could be large.
Although, the American Society for Reproductive Medicine (ASRM) had stated that it is acceptable to do sex selection (). The reason why gender selection takes place is for the prevention of genetic diseases, which is the main purpose for using PGD. Females are chosen over males is because they are less likely to hold the x-linked gene ().
‘Designer’ babies have arisen as well. Eugenics, the movement to ‘improve’ the genetic composition of humans, can be achieved by PGD. PGD gives the couple liberty to choose/change certain traits of their embryo before implanting it.
Works Cited
"Chromosome Abnormalities". National Human Genome Research Institute
(NHGRI), 2016, https://www.genome.gov/11508982/chromosome- abnormalities-fact-sheet/.
"PGD Benefits & Risks | Denver | Colorado Fertility Specialists". University Of
Colorado Advanced Reproductive Medicine, 2018, https:// arm.coloradowomenshealth.com/services/ivf/pgd/risks. Accessed 12 Nov 2018.
"PGD Testing – Procedure Cost, Risks & Benefits | Infertility Aide". Infertility Aide, 2018, http://www.infertilityaide.com/pgd-testing-procedure-cost-risks-benefits.
"Preimplantation Genetic Diagnosis: Benefits & Concerns". American Pregnancy Association, 2018, http://americanpregnancy.org/infertility/preimplantation- genetic-diagnosis/.
"Single Gene Disorders | Genetics Overview | A Look Inside Thrombotic Storm At Miller School Of Medicine". University Of Miami Health System, 2018, http:// hihg.med.miami.edu/thromboticstorm/genetics-overview/single-gene- disorders.
"Single Gene Disorders". Learn.Genetics, 2018, https://learn.genetics.utah.edu/ content/disorders/singlegene/.
"What Is A Chromosome Disorder?". Yourgenome, 2017, https:// www.yourgenome.org/facts/what-is-a-chromosome-disorder.
"What Is In-Vitro-Fertilization (IVF)?". Planned Parenthood, 2018, https:// www.plannedparenthood.org/learn/pregnancy/fertility-treatments/what-ivf.