CASE 3 YOU, FROM A TO T: YOUR PERSONAL GENOME

Your personal genome, as well as that of every human being, contains a unique combination of alleles of thousands of different genes. Most of these have no detectable effects on health or longevity, but many are risk factors for genetic diseases. Molecular studies have discovered particular alleles of genes associated with a large number of such conditions, and the presence of these alleles can be tested. More than a thousand genetic tests have already been deployed, and many more are actively being developed. A genetic test is a method of identifying the genotype of an individual. The tests may be carried out on entire populations or restricted to high-risk individuals.

The benefits of genetic testing can be appreciated by an example. Screening of newborns for phenylketonuria identifies babies with high blood levels of phenylalanine. In the absence of treatment, 95% of such newborns will progress to moderate or severe mental retardation, whereas virtually all those placed on a special diet with a controlled amount of phenylalanine will have mental function within the normal range. For recessive conditions like phenylketonuria, tests can be carried out on people with affected relatives to identify the heterozygous genotypes. Testing can also identify genetic risk factors for disease, and carriers can take additional precautions. For example, individuals with α1AT deficiency can prolong and improve the quality of their lives by not smoking tobacco, women with genetic risk factors BRCA1 and BRCA2 for breast cancer can have frequent mammograms, and those with the TCF7L2 risk factor for type 2 diabetes can decrease their risk by lifestyle choices that include weight control and exercise.

While there are many potential benefits to genetic testing, there are also some perils. One major concern is maintaining the privacy of those who choose to be tested. With medical records increasingly going online, who will have access to your test results, and how will this information be used? Could your test results be used to deny you health or life insurance because you have a higher than average risk of some medical condition? Or could an employer who got hold of your genetic test results decide to reassign you to another job, or even eliminate your position because of your genetic predispositions? There are some safeguards designed to protect you from such discrimination. The Genetic Information Nondiscrimination Act (GINA) was signed into law in 2008 and forbids the use of genetic information in decisions concerning employment and health insurance. The protection provided by GINA will, it is hoped, allow for the responsible and productive use of genetic information.

There is also increasing concern about the reliability and accuracy of genetic tests, especially direct-to-consumer (DTC) genetic tests. DTC tests can be purchased directly without the intervention of medical professionals. Since the consumer sends a biological sample and DTC tests are carried out by the provider, the tests are not regarded as medical devices and so are unregulated. One problem is that some DTC tests are based on flimsy and unconfirmed evidence connecting a gene with a disease. Another is that the link between genotype and risk may be exaggerated for marketing purposes. Yet another is lack of information on quality control in the DTC laboratories. Finally, consumer misinterpretation may regard genotype as destiny, at one extreme descending into depression and despair, and at the other using a low-risk genotype to justify an unhealthy lifestyle.