From Mandy Carranza
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ATLANTA, Georgia (CNN) -- Genetic testing can help predict many diseases and one day may help prevent them, but privacy concerns and fears of abuse could derail the technology's potential.
Genes are the basic building blocks of life. There are more than 20,000 in the human body, which determine everything from gender, to the color of hair and a person's height.
Scientists said they hope genetic information will lead to more advanced treatments in the future.
"It will make our medicines more effective, reduce the dangerous side effects; it will allow us to be on the lookout for things we need to be on the lookout for," said David Magnus, a bioethics professor at Stanford University. "It could offer a lot of help for the future."
Doctors can test blood or other tissue to check for genetic flaws that could increase the risk of disease such as cystic fibrosis, diabetes and cancer.
For example, the American Cancer Society said that a woman has a 12 percent chance of developing breast cancer in her lifetime. That risk jumps to between 50 percent and 85 percent if the woman is genetically predisposed to the disease.
The predictions are not exact, but they could inspire people to make lifestyle changes and other health decisions that could reduce their risks. (Watch why genetic testing offers hope )
But a negative test does not mean a woman won't get the disease, and some experts said a positive test could be traumatizing.
"If you have a positive test result, some patients feel that's a death sentence," said Selvi Palaniappan, a certified genetics counselor at Northside Hospital in Atlanta.
Difficult decision for patients
Margaret Scott's breast cancer was diagnosed six years ago, and she is now cancer-free. She said she wonders whether the disease runs in her family but has decided not to have a genetic test.
"Since I am not married and do not have any children yet, I didn't feel I wanted that hovering over me," Scott said.
Jeffrey Kahn, director of the Center for Bioethics at the University of Minnesota, said the decision to undergo genetic testing can be difficult.
"If you accept genetic testing information, you may learn something about your family -- some of it good and some of it potentially very troubling and traumatic," he said. "That needs to be part of the discussion as individuals go forward, or not, with genetic testing."
Debate over so-called genetic discrimination
Heidi Williams is an advocate against what she calls genetic discrimination. She said her insurance company refused to cover her children because of genetic test results.
Williams has a chronic liver deficiency called Alpha-1 that causes her body to kill the air sacs in her lungs.
Tests on her children found that they were unlikely to develop the disease but had a greater chance of passing it on to their children.
She said Humana twice denied the health insurance applications before finally extending coverage to her children.
Humana spokesman Tom Noland said that "it was a misunderstanding, not discrimination. It was a paperwork error that was later discovered and corrected." (Watch why some fear genetic testing )
A spokeswoman for America's Health Insurance Plans, which represents almost 1,300 health insurers, said she does not know of any genetic discrimination cases.
"America's Health Insurance Plans believes that genetic testing is important to help guide treatment decisions and options and to improve the quality of care," Susan Pisano said. "Our understanding is that health insurance plans do not use results from genetic tests for rate setting or underwriting."
But in 2001, in what is believed to be the largest reported case, a railroad company agreed to pay $2.2 million to settle a lawsuit alleging that it secretly conducted genetic tests on workers who filed medical claims for carpal tunnel syndrome -- a repetitive-stress injury.
In settling the case, the Burlington Northern and Santa Fe Railway Co. became one of the first firms to admit conducting genetic tests on its workers.
On the regulation front
Whatever the uncertainty over genetic discrimination, Americans have become concerned about the possible misuse of genetic information, especially in health insurance and employment.
A June 2000 Time magazine/CNN poll found that 75 percent of those surveyed wouldn't want their insurance company to have information about their genetic codes.
Some members of Congress have been working since 1996 to pass legislation that would prevent health insurers and employers from requesting or requiring genetic tests and bars insurers from raising premiums based on test results.
A bill cleared the Senate in 2005 but stalled in the House of Representatives.
Forty-one states have laws against some forms of genetic discrimination, but Kahn of the University of Minnesota's Center for Bioethics said uniform rules are needed across the country.
"What insurers can do with that information and what employers can do with that information is something we should deal with as a matter of federal policy and not leave it as a state-to-state matter," Kahn said. (Interactive: State Genetic Discrimination Laws)
Kahn predicted that patients would one day have all their genetic information encoded on a magnetic strip like a credit card to help doctors customize their treatment. (Interactive: The Future of Genetics)
Treatment lets parents achieve 'dreams'
In one area of technological advancement, doctors are using genetic testing to help parents with hereditary conditions have healthy babies.
The Reproductive Genetics Institute, a Chicago, Illinois, fertility clinic, screens embryos for diseases before implanting them in a mother. (Watch how genetic tests are preventing birth defects)
Dana and Mark Matt went to the clinic after their 17-month-old son, Kelsey, died from Zellweger's syndrome -- a genetic condition that affects brain development. Kelsey was on a feeding tube his entire short life, had to have a tracheotomy and needed a ventilator for the nine months before his death.
The Matts said they were determined not to have history repeat itself.
"There was no way for us to complete our family without the use of the genetics technology that we used," Dana Matt said.
Using the process known as pre-implantation diagnosis, the couple now have 5 1/2-month-old twin girls.
Despite the $28,000 cost of the procedure (including travel expenses), the Matts said they think they made a good decision.
"It gave us a larger family," Dana Matt said. "It's such a blessing, something we always dreamed of having but thought we never could. It's made our dreams come true."