What is Genetic Testing
Genetic testing is the process of looking at a person’s genetic makeup to determine if there are any changes or errors in the genetic material that are known to cause a specific trait/disease. These changes could be as large as the addition or deletion of an entire chromosome. Trisomy 21 (Down Syndrome) is an example of this kind of change. Or the change could be as small as a single nucleotide, as it is with the condition achondroplasia (short-limb dwarfism).
To test for a chromosomal change such as Trisomy 21, the chromosomes are visualized in a karyotype and any changes in number are easily detected (see the karyotyping lab for more information). To test for a smaller change, often a specific region or gene of the patient’s DNA is sequenced (sequence of nucleotide bases determined) and compared to a standard normal sequence for that gene. As discussed above, other types of tests can be done that do not specifically look at the genes themselves but rather at the proteins or enzymes that the gene produces or even look for restriction enzyme target sites, like what is done in this laboratory exercise.
For newborns, it is standard protocol to perform genetic testing for some of the more common genetic conditions. To find out more about the Alabama newborn screening program visit: http://www.adph.org/newbornscreening/. The site has a list and descriptions of all the disorders that newborns are currently screened for in Alabama. Genetic testing is also ordered if a baby or child is suspected to have a genetic condition that was not included on the newborn screening panel.
Later in life people may seek genetic testing for themselves for a variety of diseases. Many times a known genetic disease runs in the person’s family and they want to know if they have inherited a mutated allele and therefore have a greater chance of getting the disease themselves or passing it on to offspring. Genetic testing is commonly performed for the inherited cancer syndromes such as HNPCC and HBOC as well as many other diseases.
The New York Times produced a video interviewing a women, Katie, who has tested positive for Huntington Disease, a incurable neuro-degenerative disease. Symptoms of the disease do not usually begin until mid-adulthood. Katie talks about her decision to get tested and how her results have had an impact on her life and how she thinks about the future.
- You can view the video here:
Genetic testing is usually done by drawing a blood sample from the patient, and that blood is then sent to a specialized laboratory where the DNA is extracted and sequenced. The patient works through their doctor and genetic counselor to have the test done and the results explained to them. Currently the laboratory in the U.S. performing genetic testing for the inherited cancer syndromes is Myriad Genetic Laboratories in Salt Lake City, Utah. To find out more about Myriad and the tests they offer, visit: http://www.myriadtests.com/benefits.htm. That website also has a page of patient videos to watch about the decision to have testing for HBOC syndrome.
Ethical and Political Issues
Genetic testing brings up many ethical and political questions that need to be addressed. Things to think about include how much genetic information do we want to know about ourselves. Many agree that genetic testing is appropriate when treatment for the genetic disorder is available, but what if the disease is incurable. This issue comes up in the discussions about Huntington Disease (HD) testing. HD is an adult onset disorder for which there is no cure. There is a genetic test that will tell a person whether they will develop HD later in life. Some people who have a family history of HD decide that they want to have that information, others do not.
Another issue is about the testing of minors (<18). Protocol in the U.S. states that genetic testing of minors is only appropriate if there is treatment available that should be started while the child is still a minor. This line can be blurred for some diseases such as HNPCC where most people do not develop colon cancer until they are adults, there have been cases where children have developed polyps. This makes a case for testing of children so they can be started on routine colonoscopies if found positive.
One of the biggest issues when considering genetic testing is patient autonomy which is the idea that the decision to have genetic testing is a personal one that the patient should make for him/herself. It is important to note that two patients in the same medical situation might come to very different decisions regarding whether to test. The patient has a right to know their own genetic information but also has a right not to know. It is also important to think about how one person’s information will affect the rest of the family. Sometimes, by determining one person’s genetic test results other family members might be able to deduce their own genetic status. Just as the person who was tested has a “right” to know his results, his relative also has a “right” not to know.
Genetic Information Nondiscrimination Act (GINA)
While most Americans are optimistic about the use of genetic information to improve heath, many are concerned that genetic information may be used by insurers to deny, limit or cancel health insurance, and by employers to discriminate in the workplace. They are worried that some insurers may choose not to insure people who are healthy but genetically pre-disposed to future disease onset: such people incur more health-related costs for the insurance company than individuals who are not predisposed. Similarly, they fear that some employers might only employ or retain individuals who are not pre-disposed to future disease onset, since healthy individuals are more productive. Therefore, many lawmakers, scientists and health advocacy groups believe that there is need for federal legislation to prevent genetic discrimination.
On May 21, 2008 President Bush signed into law the Genetic Information Nondiscrimination Act (GINA) to protect Americans against discrimination based on their genetic information when it comes to health insurance and employment. The bill had passed the Senate unanimously and the House by a vote of 414 to 1. The long-awaited measure, which had been debated in Congress for 13 years, paves the way for people to take full advantage of the promise of personalized medicine without fear of discrimination.
See this website: http://www.geneticalliance.org/ginaresource with more information about GINA and its implications, definitions, and examples of genetic discrimination.