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Genetic testing you can order online
Genetic testing, billed as a way to identify your health risks, is as easy as shopping online. Before you sign up, take a critical look at what you're buying.
By Mayo Clinic staffAll your relatives on your father's side have high blood pressure. Your maternal grandmother lost most of her eyesight by her eightieth birthday — and your mother and uncle have serious vision problems, too.
For now, your own health is fine. But what about the future?
Genetic testing may look like the answer. You've seen genetic testing services advertised online as a way to assess your risk of getting a wide range of medical conditions. Just mail in a saliva sample or scraping from inside your cheek, along with a check, and soon you'll be online, browsing your own DNA.
Armed with your risk profile from genetic testing, you could take action now to avoid the health problems that plague Mom and Dad. So why not sign on?
Here's why not, at least for now. Although commercial genetic tests offer tantalizing glimpses into your hereditary makeup, the information they provide isn't all that useful for avoiding disease — and may even cause more harm than good. Find out what home genetic testing can and can't do for you and what the future might hold.
Analyzing "Snips" of DNA
Molecular genetic testing involves examining a person's DNA, the chemical database that carries instructions for making all the proteins your cells need to carry out your body's functions. Genes are the segments of DNA that carry a particular set of instructions. There are approximately 30,000 genes that make up the DNA strands in each of your cells, your genome.
Genetic tests have been used for years to identify specific genetic changes known to be associated with a particular disease. Testing laboratories currently perform more than 1,100 different genetic tests. These tests serve many purposes, from screening newborn babies for hereditary disorders to diagnosing inherited cancer syndromes.
What's different about the new commercial genetic tests? They use DNA microarray technology to evaluate the genome for hundreds of thousands of points of difference in a person's DNA rather than just a few specific genes. These tiny differences in gene sequence are known as single nucleotide polymorphisms, or SNPs, pronounced "snips."
Researchers have identified over a million SNPs and correlated some of them to disease risks, physical and other traits. And a whole category of SNPs, useful for geneaologists and anthropologists, holds information about where your ancestors came from. On the other hand, the clinical significance of many SNPs is not known.
Limitations of genetic testing
The genetic tests you can order on your own don't tell you whether you have or will get a particular disease. They can only give you your estimated odds of developing each one of a number of common diseases — and only to the extent that the presence or absence of a few SNPs tells the whole story about your risk. Most of the time, individual risk is much more complicated than that.
Many common diseases, including heart disease, cancer and diabetes, have complex genetic underpinnings — they don't stem from a single altered gene or SNP that can easily be identified. Rather, they involve interplay between multiple genes, as well as environmental factors.
Genetic tests based on SNPs assess only a limited number of gene variants associated with any given disease. But for most diseases, researchers are still in the early stages of identifying the full list of gene variants that may make a person susceptible. In other words, if you have a gene profile that's linked with a higher risk of, say, osteoporosis, it doesn't mean you'll actually get this disease. Equally important, not having that genetic susceptibility profile offers no guarantee that you won't get the disease.
What's more, SNPs account for a relatively small part of the genetic variation among individuals. There are other genomic variations, not detected by microarray technology, that may have a greater effect on disease risk than any single SNP.
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