Genome Scans and Genetic Testing
Part 2

Q. What is genetic counseling?

A. Genetic counseling provides information and support to people who have, or may be at risk of, inherited disorders. A genetics professional (medical geneticist, genetics counselor, or genetics nurse) discusses your risk with you and may or may not suggest genetic testing.

Genetics professionals:

• Assess your risk by looking at your family's health history and medical records.
• Provide support and information to help you decide whether to be tested.
• Explain what the results of genetic tests mean.
• Provide counseling or refer you to support services.
• Explain options for treatment or prevention.
• Explain how test results could affect decisions about having children.

If your test shows that you do have a genetic variation clearly associated with a specific disease, you may be referred to a doctor or researcher who specializes in that illness. Both your primary care provider and a genetics professional can help you with decisions about testing and can help you interpret your test results.

Some genetics professionals specialize in a disease category (such as cancer), age group (such as adolescents), or type of counseling (such as prenatal).

Q. Are there risks associated with genetic testing?

A. Some people who know they're at risk of a serious disease, because the disease runs in the family, avoid having genetic testing. They're afraid their insurance companies or employers will drop them if tests show they have the gene variation that may lead to the disease. They fear they might have trouble getting insurance or a job.

As of March 2008, efforts are underway to enact federal legislation that would make it illegal to discriminate on the basis of genetic test results.

For the rare, single-gene diseases, genetic testing is important. It leads to early detection and therapy for these diseases.

Q. What can research about gene variations tell us about disease risk?

A. As they continue to discover combinations of gene variations and external factors that contribute to specific diseases, scientists are building a more complete picture of how to detect which people are at risk of common diseases.

This research also is helping to reveal the biological pathways through which gene variations contribute to disease. Scientists can use this information to design better screening and prevention for specific diseases, and find more precise molecular targets at which to aim as they develop new medications.

Family History Gives You Good Clues About Your Risk

Your family history is one of your best clues about your risk of developing many common illnesses, including mental disorders.

For example, bipolar disorder and schizophrenia tend to run in families. At this time, no type of genetic testing can tell you whether or not you will develop mental illnesses. Not enough is known about which gene variations contribute to them, or the degree to which other factors contribute.

For now, your family history may be your best indicator. For example, studies show that if you have a close relative with bipolar disorder, you have about a 10 percent chance of getting a mood disorder, such as bipolar disorder or depression.1

Now consider what the gene variations scientists have linked to mental disorders, so far, can tell you about your risk. Even the variations with the strongest ties raise the risk by only very small amounts. Knowing that you have one of these variations won't tell you nearly as much about your risk as your family history can.

Family history also provides a good clue about your risk of rare diseases that can be detected through genetic testing. If one of these rare diseases, such as cystic fibrosis, runs in your family, your risk is likely very high.

If a disease runs in your family, your health-care provider can tell you if it's the kind of illness that can be detected through genetic testing at this time. Your provider can help you make decisions about whether to be tested and can help you understand test results and their implications.

1 Gershon ES, Hamovit J, Guroff JJ, Dibble E, Leckman JF, Sceery W, Targum SD, Nurnberger JI Jr, Goldin LR, Bunney WE Jr. A family study of schizoaffective, bipolar I, bipolar II, unipolar, and normal control probands. Arch Gen Psychiatry. 1982 Oct;39(10):1157-67. PMID: 7125846.

What Are Genes?

Genes are pieces of DNA, in cells, that parents pass down to their children at conception.

Genes turn on and off throughout life to transmit chemical instructions for making the body's proteins. Proteins are part of what gives us our characteristics; for example, our height, eye color, personality, and our chances of getting specific diseases.

Genes can have slight differences in their structure from person to person, and these variations can cause differences in people's characteristics. Gene variations help explain why members of the same family often look alike and have other characteristics in common, such as certain illnesses - because each child inherits a mixture of both parents' gene variations.

Some gene variations make people more vulnerable to different diseases, and some have protective effects against different diseases. Some rare diseases are caused by variations in a single gene.

Most common diseases are caused by a mixture of many gene variations, some unknown, and external factors, such as stress or toxic substances.

Some gene variations appear to have no effect on risk of disease.