Genetic Testing - What It Is and What It Can Do for You and Your Family

James Zubernis, DO
Hamilton Obstetrics and Gynecology
A Service of Marcus Daly Memorial Hospital
1200 Westwood Drive
Hamilton, MT 59840
(406) 375-4777

Genetic Testing - What it is and what it can do for you and your family.

The Human Genome Project was started in 1990 and completed in 2003. The goal of the project was to map the DNA of human beings. DNA is the "map" which allows our species to reproduce and has the information for the development of a person from conception and throughout life. DNA contains the information that is necessary for our bodies to function and is the cause for the development of diseases that can be passed from one generation to the next.

One of the major benefits derived from the Human Genome project was the identification of which genes are responsible for the development of many diseases such as breast cancer, ovarian cancer, colon cancer and many others.

Once you know which genes cause a disease, a test can be devised that can test an individual for the presence of the gene.

Some of the earliest genetic testing available was for the gene that causes breast cancer termed BRCA1 and BRCA2 for breast cancer gene 1 and breast cancer gene 2. Many other cancers can also be tested, since the genes that are associated to specific cancers have been "mapped" and tests have been developed for them.

It should be noted that if you test positive for a specific disease it is not a guarantee that you will develop the disease but suggests that you might have a predisposition for the development of the disease.

Knowing that information allows doctors to identify individuals who are at risk and to put interventions in place that will identify those who go on to develop the disease and intervene early.

One example of these interventions is early colonoscopies for people who have a gene for familial polyposis, a condition that is at high risk for the development of colon cancer. Early colonoscopy allows doctors to remove polyps that are pre-cancerous or harbor an early cancer before the disease can spread to other parts of the body.

Another example of intervention is for those individuals who test positive for the breast cancer gene. Since the BRCA1 and 2 gene can be associated with cancer of the breast, ovary and uterus, many women who carry the gene have opted to undergo mastectomy (removal of the breast), hysterectomy (removal of the uterus) and oophorectomy (removal of the ovaries) as a way to guarantee that they will be protected from the development of a cancer in these organs.

These genetic tests are based on similar technology that has been used in prenatal diagnosis. Patients who have a family history of cystic fibrosis may want to be tested for the presence of the gene. If both parents have a copy of the gene, their offspring will have cystic fibrosis; Cystic Fibrosis (CF) can affect the lungs, pancreas, liver, kidney and intestine. People who have full blown CF have difficulty with lung infections and other lung problems and contribute to 80% of the deaths of patients affected by CF. Patients with full blown CF tend to have much shorter life spans and the average age of death is between 42 and 50 years of age.

Newer technologies for genetic diagnosis come in the form of a procedure that tests maternal blood for cell-free DNA. This is DNA that is shed by an unborn baby into the mother's bloodstream and can be tested by drawing blood from the pregnant woman. These tests allow for identification of birth defects like Down's syndrome and Trisomy 18. It can also identify the gender of the baby.

For other types of genetic testing, either a blood sample or a swab from the inside of your cheek can be used to obtain DNA.

Clinicians are using genetic screening to help properly prescribe medication by identifying individuals who may metabolize some drugs faster than other people. This may mean that an individual needs to be on a higher dose of a medication than individuals who metabolize normally.

The applications of these genetic tests are really just being developed and genetic testing will allow for earlier identification of people who are at risk for many diseases. Early identification allows for specific interventions that remove the parts of the body that may develop a cancer. It can identify individuals who might be at greater risk for the development heart disease, high cholesterol, diabetes and other metabolic disorders. For those individuals that have the genetic make up to develop these problems your physician may be able to recommend lifestyle modifications, medications or other therapies to reduce your risk of having a problem before it occurs.

There are more than 2000 tests for 1000 different diseases available. A good rule of thumb to know if you are at risk for a genetic disease is to look at your family history. If there are several people who have developed a particular disease in your family then you may carry the gene for that disease. In the past doctors knew that family history was important but with genetic testing specific diseases can be tested for and managed.

Talk to your family doctor or primary care physician about genetic testing. Many tests are being covered by insurance and as more companies develop tests, the overall cost will become affordable for most people.

Questions and or comments regarding this week's health column please contact, James Zubernis, DO at Hamilton Obstetrics and Gynecology, a service of Marcus Daly Memorial Hospital, 1200 Westwood Drive, Hamilton, MT 59840. Working together to build a healthier community!


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