What is Informational Genetic Testing?
Informational genetic testing refers to testing for genetic variations that are not typically used in clinical practice by physicians and genetic professionals to diagnose disease or establish disease risk. While some types of informational genetic testing, such as ancestry testing and DNA-based identity testing, are not related to disease at all, other types, such as SNP testing and whole genome scanning, test for genetic variations called SNPs recently linked to common diseases.
What is a SNP?
DNA is made up nucleotides - chemical compounds consisting of a base, sugar, and phosphate. Bases are similar to letters of the English alphabet. Only instead of 26 letters, there are only four: adenine (A), guanine (G), cytosine (C), and thymine (T). These four “letters” when combined in different sequences make up our genetic code. A single nucleotide polymorphism, or SNP (pronounced "snip"), occurs when a single nucleotide, such as an A, replaces one of the other three nucleotide letters - C, G, or T.
Within the approximate 3.2 billion nucleotide human genome sequence, there are an estimated 10 million SNPs. The identity of these SNPs, along with other less common forms of genetic variation, are essentially responsible for making us genetically unique. For a single-nucleotide variation to be officially considered a SNP, it must occur in at least 1% of the general population.
Only about 3% to 5% of our total DNA sequence actually codes for the production of proteins ("coding sequence"). Proteins perform different biological functions in our body. Most SNPs are found outside of "coding sequences" and therefore, are less likely to affect biological functioning. SNPs found within a coding sequence are more likely to affect the production and function of a protein. Many of these SNPs may be responsible for our differences in physical appearance, susceptibility and resistance to disease, response to medications, and other human traits.
SNPs and Disease Risk
Because of recent advances in genetic technologies, there has been increasing research focused on the identification of SNPs and their association with disease risk. Many researchers believe this research will help them identify the multiple genes associated with complex, multifactorial conditions, such as breast cancer, diabetes, autoimmune conditions, heart disease, and mental illness. Multifactorial conditions are caused by a combination of genetic, environmental and lifestyle factors. As such, a person's overall risk to develop these diseases is very difficult to quantify and evaluate.
Regarding the genetic risk factors, they themselves are often difficult to establish because multiple genes likely interact to cause susceptibility or resistance to disease as well as affect the severity or progression of disease symptoms. In addition, multiple genes likely interact to affect the metabolism of medications used to treat complex diseases.
We are just beginning to learn how SNPs can provide insight into these genetic risk factors.
Much research is still needed to clearly establish associations between most SNPs and disease susceptibility. The results of initial studies with a small sample size (number of people tested) need to be confirmed in multiple studies with large sample sizes in order to be considered statistically significant. In addition, studies that involved only people from a particular ethnic background need to be validated in populations from a different ethnic background or in a multi-ethnic studies.
In the meantime, many health professionals believe that the results of most SNP testing are not medically (clinical) useful.
Over time, with more research, the implications of SNPs on disease risk will become clearer. The goal of researchers is to one day be able to use a person's total genetic information to better predict, prevent, and treat disease.
SNP Testing
Some direct-to-consumer (DTC) genetic testing providers have begun offering SNP testing over the internet (online) for certain common diseases. Some providers have referred to this testing as "Genetic Risk Analysis" Testing. Each provider has developed their own internal guidelines, policies, and standards regarding which SNPs they test for and how well researched the SNP must be before they offer testing.
- For example, while one provider will test for three SNPs linked to a particular disease, another will test for only one, and yet another, none at all. There are no official regulations or guidelines on how well researched and validated a SNP must be before testing is made available. This has led to much debate within the genetic community over the accuracy, validity and reliability of this testing, as well as criticisms of the testing providers themselves. Many physicians and genetic professionals are hoping that stronger rules, regulations, and policies will soon be established.
In addition, some DTC providers offer whole genome scanning which analyzes hundreds to thousands of SNPs at the same time linked to multiple common multifactorial diseases and/or traits, such as hair color and eye color. More information about individual DTC providers can be found by searching by provider name or by a genetic test they offer.