Реферат: Genetic Screening Essay Research Paper Genetic screening
Genetic Screening Essay, Research Paper
Genetic screening, also known as preimplantation genetic diagnosis (PGD), is a newly emerging
technology that has brought with it much controversy. PGD involves the in vitro fertilization of an
embryo. ?The embryos are allowed to develop to a 6 to 10 cell stage, at which point one of the
embryonic cells is removed from each embryo and the cellular DNA is analyzed for chromosomal
abnormalities or genetic mutations? (Botkin, 1998). In doing this, it can be determined which
embryos will be most likely to implant and germinate successfully in the uterus. PGD is a
complicated, technologically sophisticated process. It is a union of in vetro fertilization
technology and molecular biology (Botkin, 1998). Though it has numerous positive attributes,
there are equally as many negative ones. In fact, this issue is one that has recently become the
subject of many heated debates. Proponents for the use of PGD assert that this test allows for
parents with fertility problems to maximize their opportunity for conception and birth. Their
adversaries argue that this process is morally questionable, and though it is seen as safe alternative
to abortion couples can experience the same psychological effects as if they were dealing with an
actual abortion (Botkin, 1998). Obviously, this is an issue that does not have one distinct answer.
Each opposing side has raised some poignant arguments.
Those who are in favor of PGD generally use the arguments that it allows for the
transmission of human genetic diseases to be reduced (McClure and Tasca, 1998). Before the
usage of PGD the only other way to determine the existence of genetic diseases was by the use of
prenatal diagnosis in the form of amniocentesis or chronic villus sampling (CVS). Currently, CVS
can only be performed in the ninth to eleventh week of pregnancy, and amniocentesis can be
performed in fifteenth to eighteenth week (McClure and Tasca, 1998). At this point, the fetus is
developing within the uterus. Discovery of any abnormalities would pose the parents of the fetus
with a difficult decision. They either continue a pregnancy that will result in a genetically defected
child or abort the fetus. This is where PGD allows for what some would say an easier option.
Because PGD is a pre- pregnancy test, abnormalities can be detected prior to the embryo ever
being inserted into the mother. Currently, there are several diseases that PGD can detect such as
Cystic Fibrosis, Tay-Sachs disease, Duchenne Muscular Dystrophy, Fragile X Syndrome, and
Down Syndrome (McClure and Tasca, 1998). These are only a few of the diseases that can be
detected but as the knowledge concerning human DNA increases there will be more detectable
diseases. In addition to disease detection, PGD can also detect the gender of an embryo which
can enable the determination of the existence of sex-linked disease or a sex chromosome
imbalance (McClure and Tasca, 1998). Another of PGD?s benefits is its ability to assist women
over the age of thirty-five to successfully conceive. From this age group 50 percent of the
embryos are chromosomally abnormal (McClure and Tasca, 1998). For these women, PGD
drastically increases the odds for a successful pregnancy while the odds for miscarriage are
reduced (McClure and Tasca, 1998). PGD also has promising outlook in cancer research. In the
same manner that PGD detects single gene defects in embryo tests, it could do the same for
polygenic diseases such as cancer (Yates, 1996). Experiments with genetic screening have been
done concerning Tay-Sachs disease .The outcome of this research indicated that PGD has the
potential to be extremely beneficial. Tay-Sachs disease affects 1 in 3600 Ashkensasi Jews, couples
who were at risk for transmission of this disease to their offspring were genetically screened (
Robbers, 1990). As a result of the screening, the number of children who were born with
Tay-Sachs disease dropped from 50 in 100 in 1970 to 13 in 100 in 1980 ( Roberts, 1990). Due to
the positive results from genetic screening, it is becoming somewhat more popular and accepted.
In a survey done by Johns Hopkins School of Public Health, a group of people were surveyed to
determine their likelihood to undergo genetic screening given their family history concerning
colon cancer (Henderson, 1999). Those who had a significant family history of colon cancer as
well as those who did not were eager to undergo gene testing (Henderson, 1999). At this point,
genetic screening has begun with a good track record. Most of those who have used it or heard
about it are positive about its real or anticipated results. PGD seems to be a promising medical
procedure, but as always with new things there are doubters and skeptics.
One of the many negative statements that the adversaries of PGD use is that it may cause
women the same psychological effects as she would experience with an abortion. The embryos
that are found to have abnormalities are usually destroyed just as a fetus would be destroyed.
Currently, there has been no research concerning the psychological reactions to PGD so this is a
real concern. The techniques used for PGD requires that several embryos be used. In a recent
report, twelve couples utilized PGD to screen for cystic fibrosis. The couples produced 137
embryos, of which 26 were transferred to a woman’s uterus and 5 births resulted (Botkin, 1998).
The loss of prenatal life was greater through PGD than would have resulted had the twelve
couples used traditional prenatal diagnosis and selective termination (Botkin, 1998). For most
couples, two cycles of egg retrieval, testing, and implantation usually are required to establish a
successful pregnancy (Botkin, 1998). For any individual couple, PGD requires several months of
time, multiple drugs, invasive procedures, and specialists at a center for reproductive
medicine(Botkin, 1998). Once a pregnancy is established, traditional prenatal diagnosis is still
recommended to check the process (Botkin, 1998).This complicated process is also an expensive
one. Couples who choose to use PGD would have to be willing to spend in excess of 43,000
dollars because as of now 85 percent of the costs of in vitro fertilization are not covered by
insurance companies (Botkin, 1998). This figure does not include the PGD procedure, couples
would be spending a large amount of money to use these techniques. For women over thirty-five
the usage of PGD would not only be expensive but very risky. These women would only have
approximately a 5 percent chance to become impregnated using PGD and in vitro fertilization
(Botkin, 1998). With the procedure being so expensive, the combination of PGD and in vitro
fertilization will only be used by a select few. The users will be limited to couples who can afford
this expensive procedure, and couples who are selected by researchers to have the process
institutionally funded. Not only is the process expensive, but it also has the potential to be
unreliable. As previously mentioned, PGD is still a new medical discovery, there is still an element
of risk involved in its usage. The major risk is misdiagnosis. There is a strong possibility for
technical error in this process. The entire procedure, including PGD and in vitro fertilization,
involves six separate technologies (McClure and Tasca 1998). When the embyro?s cells are
actually removed there is a chance that chromosomal abnormalities may not show up even if they
exist. The embryos are in such a primordial state that all of the cells may not yet have the
abnormality. Potentially, an abnormal embryo may be implanted in the uterus. Even after usage of
PGD and in vitro fertilization the percentages of the frequency of babies born with birth defects
among those who use it and the general population is 3 percent for both groups(McClure and
Tasca 1998). Aside from these problems there is also the issue of the regulation of genetic
screening. Many people fear that in the future genetic screening will not only be used to prevent
children being born with chromosomal abnormalities but also that it may be used for physical and
psychological selection of embryos. Obviously, there are going to be problems with any new
medical procedure. PGD is still in its infancy, with time and research there will still be problems,
but hopefully they can be decreased.
The usage of PGD is bound to be surrounded by controversy. Anything that can
potentially involve genetic selection is naturally of concern to our society. The important thing to
do is exercise sound decision making concerning its use. There is no doubt that there are risks in
using PGD but there are risks in using any medical procedure. Research indicates that some
couples have had success in using PGD and in vetro fertilization while others have not. By their
very nature, PGD and in vetro fertilization are tests that have a natural probability of not
succeeding. The key to using these procedures in knowledge. Couples need to know the
advantages as well as the disadvantages that go along with these procedures. Concerning the
matter of genetic selection, there needs to be some strict regulation. If PGD is used for the wrong
reasons there could be serious damage done to our society. After we take away all of the medical
jargon, the fact is that our society needs to exercise positive decision making techniques to
maximize the benefits of this new medical breakthrough.
Botkin, J. (1998). Ethical issues and practical problems in preimplantation genetic diagnosis.
Journal of Law, Medicine, & Ethics, 26, 17-28.
Henderson, C. (1999, May). People lean toward genetic testing, risk aside. Cancer Weekly Plus.
McClure, M. & Tasca, R. The emerging technology and application of preimplantation genetic
diagnosis. Journal of Law, Medicine, & Ethics,26, 7-16.
Roberts, Leslie. One worked: the other didn?t. Science, 247, 18.
Yates, John. Medical genetics. British Medical Journal. 312, 1021-1026.