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
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.
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