Scientific and Ethical Considerations of DNA testing

DNA Testing; Scientific and Ethical Considerations.

DNA testing was first used in the 1970s. It is when DNA is taken from a subject and then tested using different techniques developed over the years to map out the sequences and use the information in a variety of ways, like provide information on a person’s underlying genetic makeup or genotype. DNA tests have developed from early DNA testing to predicting the development of genetic disorders, screening for traits and population screening to provide insight into future conditions and health of the person, confirming and backing up clinical diagnosis, prenatal testing and DNA testing to hone in on the specifics of conditions and individualise treatment. (1)

Methods for DNA Testing

There are many forms of analysing DNA starting with the earliest there was Restriction Fragments Length Polymorphisms (RFLP) analysis which used DNA fragments separated into bands by size to find the difference between samples of homologous DNA molecules from different locations of restriction sites. The DNA sample is digested by restriction enzymes and the fragments are separated according to size by gel electrophoresis. But this was replaced due to time constraints and needing large amounts of DNA. (2, 3, 4)

Another Method of testing DNA is Polymerase Chain Reaction (PCR) this analysis uses specific parts of the DNA strand to amplify small amounts of a specific piece of DNA. The method uses thermal cycling which is the repeated heating and cooling do this DNA is broken into single strands and enzymic replication can occur of the DNA, it uses primers which are short pieces of DNA fragments which are complementary to the target region and with DNA polymerases select and amplify the DNA fragment and these fragments become the template for further amplification so therefore producing a chain reaction which exponentially amplifies the DNA fragment. However because this method is very specific it cannot distinguish between mixed samples. (2, 3, 4)

Another method of DNA testing is Amplified fragment length polymorphism which uses PCR to amplify DNA fragments, but used variable number tandem repeat polymorphisms to distinguish various alleles separated by polyacrylamide gel comparing against an allelic ladder. The bands produced were seen by silver staining the gel. It is an easy and low cost method of DNA testing. (5, 6)

Also a method which is the most popular and used most often in DNA testing is Short Tandem Repeats (STR) and uses PCR to amplify the fragment and then uses short tandem repeats and is used on highly polymorphic regions that have short repeated sequences of DNA, this principle works on the fact that people have different repeated units, so the STRs can distinguish between different peoples samples. The regions of STR are targeted using specific primers and amplified with PCR and the DNA fragments are separated and detected by electrophoresis. (7, 8, 9)

Another method in this case which targets the Y- chromosome markers on the male part of the sample, which is done by the production of primers targeting polymorphic regions on the Y-chromosome (Y-STR) and allows the separation of mixed samples from male and females. (10)

Finally there is Mitochondrial Analysis which is used for testing highly degradable samples where instead of DNA samples being tested which are sparse in the sample; the Mitochondrial DNA (mtDNA) is tested because there are more copies of this type of DNA in a cell. The forensic scientists amplify the HV1 and HV2 regions of the mitochondrial DNA and sequence each region and compare single nucleotide differences. This is useful because mtDNA is inherited and so relatives can be used as match references. (11, 12)

DNA Testing Uses.

These tests can be used to detect susceptibility of one particular disease which may be prominent in their family’s history. To show any symptoms which are occurring or the passing of this genetic material to their off spring in the future may occur. It also can look at legitimacy of birth of a child, and tests can detect more social aspects like behaviour and sexual orientation. DNA testing is also used for paternity testing to assess the farther of the unborn child or born child, also can be used to match organ donors with recipients in transplant cases. (13)

DNA testing can be used by the genetic councillor as a source to find out if one or both the parents of the child are carriers of a genetic disorder usually done to families with a history of recessive genetic disorders who are having or consider having a child, the most common genetic diseases which are tested for are Cystic fibrosis, Tay-sacs disease and sickle cell trait. This will affect the families in many ways so ethically is this right? Other uses are to diagnose any prenatal risks by testing the foetus for any genes which may predispose the child to mental retardation or physical deterioration like Down syndrome which will have an effect on the parents to keep the child or abort. Another use in children is screening the newborns for diseases like Phenylketonuria and congenital hypothyroidism and this is done as a prevention method to cure or treat the child at the earliest stage possible. Also Late onset disorders can be tested which are diseases that affect adults like cancer and heart disease, which are difficult to pin point the causes which can be nature or nurture, from the genes or from the environment like diseases that can be found that are affected by a change in one gene which can give the disorder like Huntington’s disease but in this case can be tested for throughout life at any stage of time. (14)

Recently the government has made new initiatives to explore more means of identifying a person using different markers and producing profiles like DNA fingerprinting which come from the results of DNA testing to identify unique characteristics of a person which are further used by the legal system for cases of paternity and criminal identification as well as in the time of major disasters and accidents or in war for the identification of soldiers and civilians which have died. (14)

Ethical Considerations

Ethics are guidelines to which many issues can be resolved to protect an individual from being taken advantage of by anyone trying to take information from them and also creates morality to not harm anyone. The ethics in DNA testing significantly coincides with the medical ethics and the use of personal medical information. However in DNA testing there are more important aspects of ethics greater than in just protecting the medical information, because the knowledge of genetic information can affect family members because of the information of their health status disease risk and possible transmission to offspring which makes the ethics surrounding DNA testing a lot more imperative. (15, 16)

A specific example of ethical consideration can be looked at in the study of Huntingtons chorea.

Huntington’s chorea is a dominantly untreatable, progressive and lethal disease. The patient suffers extreme distress, however when diagnosed the majority of the burden besides to the relatives who have to cope with the mental and physical deterioration of the patients whilst realising that they and their children are at risk. (18) The nature of this disease is there are variable ages of onset therefore those at risk will not know their genetic state until after they have completed their family or the non- carriers have to wait until late middle ages before they can be free of any risk of developing the disease. (19)

So if anyone wants to find out whether they are at risk they need to get a DNA test done which in this case is also known as a predictive test but this test causes some ethical problems. Firstly does the test have a high percentage accuracy and is there any inaccuracy related to the test. In this case this test is used by the patients to make important decisions about their future and so there is a need that inaccuracy of the test is known so that lives don’t radically change for no reason. To know your risk factor and the accuracy of the test you need to know that the test is testing the right thing in this case is Huntington’s chorea always caused by a mutation at a locus genetically linked to G8 or is there other forms of the disease, showing that testing for the G8 may be misleading. (19)

Secondly is the possibility that when a person is identified as gene carrier they may not be able to cope with the burden of this revelation. But if you were found not to be a carrier then this test will benefit you a lot, however the patients who have been identified as carrier they may be deprived of hope of living a normal life and may become depressed or contemplate suicide. (20)

Research shows that the appearance of psychiatric disorders is high among those who develop Huntington’s chorea, (21, 22) therefore a shown increased in suicide in some families. (23)

So a disadvantage of the predictive testing shows that psychopathology in the people who at risk is caused by the knowledge they are at risk of Huntington’s chorea and not the primary genetic cause and that uncertainty is better that certain knowledge that you may get Huntington’s chorea. (24) However it has been looked at that early diagnosis will give time for the patients to prepare emotionally and financially so that when Huntington’s chorea symptoms occur they are aware and prepared. (25, 26) Overall depending on your view the predictive tests may increases or decrease the prevalence of suicides. (19)

Lastly the issue of the possible misuse of the information received from these tests. Mainly the fact that the information gained from the tests will be of interest of others apart from the person at risk so therefore may lead to complications. Like if the spouse wants to know if there partner doesn’t want to know if they have Huntington’s chorea. Also if a parent is identified as a gene carrier then the child is at risk and so they might not want to know this information. But there is also the scenario whereby the family member wanting the test needs another family member to agree to be tested too, so pressure may be put on this family member to get the test done. With respect to this other organisations like pension funds, insurance companies and prospective employers may demand this information before a post is given. (27) Similarly problems may come before marriage where one person puts pressure on to the other to be tested or because of a sense of obligation wants to be tested for the person at risk. (19)

From these views it can be established that there are many ethical considerations and that in this case of predictive testing that a code of practice should be developed, with rules and guidelines like predictive tests shouldn’t be offered to minors or used in cases where a carrier is identified who didn’t want to know. Also those insurance companies and others with financial interest should be precluded by law from asking for information on carrier state. (28)

Problems may be diverted using selective counselling techniques before testing, so that the subject is well aware and fully informed of the meanings and limitations of the results and is proved with enough support after testing so that it doesn’t all come as a shock and that the person is eased in and out of the testing and the new information and knowledge which has been learnt from the testing. This counselling is needed so that testing is done with full informed consent and provided with unbiased and impartial and with no obligations or external pressure and the decision is wholly theirs. (19)

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