Why genetics is interesting

The demand for genetic risk assessment and counseling, incidentally, may exceed what might be expected based on the frequency of this group of disorders. For every individual who is at risk for breast cancer due to BRCA1 mutation, for example, there are probably several who have a relative with breast cancer and think that their risk is increased.

These people may not need to have genetic testing or surveillance for disease, but they may benefit from meeting with a counselor to get an accurate assessment of risk.

The outcome usually will be reassurance; occasionally it will result in testing and the subsequent institution of a management program. The approach to this group of disorders is in rapid evolution and will likely see major changes in the next several years. First, many additional disorders are likely to be added to the list.

The identification of the major genes for breast and ovarian cancer spawned a rapid demand for counseling and testing. Will the same thing happen when genes for psychiatric illness are identified? Second, advances in information technology are likely to have a major impact on the care of these disorders. Physicians will increasingly need to use computers to access medical information about their patients, to recognize patterns that require intervention, and to access testing and referral services as well as patient information material.

Furthermore, patients themselves are increasingly turning to computer resources, especially the Internet, for medical information.

It seems likely that counseling and testing services may at some point be available directly to patients, without the intermediary of their primary care physician. A third change that might be anticipated concerns the ethical context in which genetic information is used in patient care. There is major concern now about the risks of loss of privacy and discrimination. Some of this has been addressed through passage of laws that ban at least some use of genetic information for employment or insurance.

National legislation remains unenacted. It is not clear that the issues raised by genetics are really unique in medicine, but genetics is drawing attention to these issues and will likely drive responses both in terms of legislation and regulation. A final change concerns the public health implications of genetics in medicine. There is a long history of public health initiatives in genetics, particularly in the area of newborn screening. As testing becomes possible for genetic causes of common disorders, and especially as interventions become available, there is likely to be increasing attention given toward the possibility of wide-scale screening.

Genetics will become truly integrated into medical practice when the genetic contributions to common disorders, such as diabetes or cardiovascular disease, are understood and can be used to improve the quality of care.

Although most of these disorders include rare single gene causes see above , most are due to an interaction of multiple genes and environmental causes. A large number of genes may be involved in any particular disorder, and the specific genes involved may differ from one individual to the next. Some genes will contribute substantially toward risk; others will make a slight contribution. Genetics will be important not only to understanding the cause of a disease, but also to recognizing the manner in which an individual responds to particular therapies.

Drug metabolism is itself under genetic control, and susceptibility to side effects in some cases is governed by genetic predispositions. A scheme for thinking about the genetic contribution to common disorders is presented in Figure 1.

Individuals inherit genes that may predispose them to disease but will only develop the signs and symptoms if exposed to appropriate environmental factors. Chance may also play a role in determining whether an individual who is at risk becomes symptomatic. Genetic testing may have a role both in the presymptomatic phase and after signs and symptoms have emerged.

Individuals are born with a genetic liability to disease but remain in a presymptomatic state until exposure to environmental factors leads them to cross a threshold into recognizable disease. The y axis depicts progression from prenatal life to a presymptomatic state to a state in which disease is present.

Presymptomatic genetic testing raises many controversial issues, both technical and ethical. In some instances, genetic test results may contribute very small increments of relative risk, which may not provide guidance for management.

There is a risk of overestimation of penetrance from databases on ascertainment of families in which many individuals are affected, and it may be many years before the risk of disease in a carrier is known. Despite all these challenges, however, it is likely that at least some disorders will be subject to presymptomatic testing, particularly where early treatment improves the natural history. Genetics may have its greatest role in the care of individuals with common disorders in the realms of diagnosis and therapy.

Identification of genes that contribute to these conditions, even if they convey only small increments of risk, will reveal pathological mechanisms that may have been previously unsuspected. This, in turn, will provide an opportunity to develop new approaches to therapy, in some cases by the design of new drugs that target particular cellular pathways.

Choice of therapy may, at some point, be guided by genetic tests that identify subcategories of disease that will respond to specific treatments.

Drug dosage may be influenced by tests of drug metabolism polymorphisms, and serious side effects may be avoided by avoiding the use of specific drugs in individuals at risk. Most of these changes will have their greatest impact on the day-to-day practice of medicine by primary care providers and by medical specialists. Physicians may one day make treatment decisions based on tests without realizing or needing to know whether the tests are based on analysis of DNA, proteins, or other markers.

The role of the medical geneticist for common disorders is likely to be more in the background than for the other categories of disease. There will always be a subset of patients with multisystem disorders with a significant genetic component for which the medical geneticist will be able to provide comprehensive assessment.

But for most of the common disorders, the geneticist will play a role in the development of testing systems and the interpretation of test results. We have created a matrix that is shown in Table 1. The integration of genetics into medical practice will occur at a variable pace for different disorders and in different areas of medicine. Home Undergraduate. Why study Genetics? Department of Genetics Undergraduate Why study Genetics?

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