Genetic testing offers a window into our DNA, the biological blueprint that influences our appearance and predisposition to certain health conditions. As technology has advanced, different types of tests have become available for analyzing our genetic code. One of the most common approaches focuses on tiny, specific variations within the genome.
What Are Single Nucleotide Polymorphisms
Imagine the human genome as an encyclopedia written with only four letters: A, T, C, and G. While nearly identical between any two people, you might find that at a specific location, a single letter is different. This single-letter difference is a Single Nucleotide Polymorphism, or SNP (pronounced “snip”), the most common type of genetic variation.
For example, where most people have the letter ‘C’, an individual might have ‘T’. The human genome contains millions of these variations. While most have no impact on health, some can influence physical traits, drug responses, and susceptibility to developing particular diseases. These SNPs are not errors but are variations that contribute to human diversity.
The SNP Testing Process
The process begins with sample collection, which involves swabbing your cheek or spitting into a collection tube. This gathers thousands of your cells, containing a complete copy of your DNA. The sample is then sealed and sent to a laboratory for analysis.
At the lab, DNA is extracted from your cells. The testing process uses a technology called a SNP chip, a small glass slide containing millions of microscopic probes. Each probe is engineered to detect a specific, known SNP from the human genome.
Your extracted DNA is washed over this chip, and the fragments bind to corresponding probes. A computer then scans the chip to read which probes your DNA has attached to. This process reveals your specific version, or allele, at hundreds of thousands of predetermined SNP locations.
Information Revealed Through SNP Testing
SNP testing can unlock a wide range of information encoded in your genome, offering insights into your heritage, health risks, and how your body might interact with certain substances. Key applications include:
- Ancestry composition: Certain SNPs are more common in people from specific parts of the world. Analyzing these patterns can estimate the percentage of your ancestry from different global populations.
- Health predispositions: The testing can identify SNPs associated with a higher or lower chance of developing certain conditions. This information indicates a statistical probability, not a definitive diagnosis.
- Pharmacogenomics: Specific SNPs can influence how your body metabolizes certain medications. This can help determine a drug’s effectiveness or the likelihood of experiencing adverse side effects.
- Carrier status: Carrier screening can show if you have one variant for a recessive genetic disorder that you could potentially pass on to your children.
- Physical traits: On a lighter note, testing can also reveal your genetic likelihood for various traits, such as eye color, lactose intolerance, and caffeine metabolism.
Interpreting SNP Test Results
Testing companies present findings in a user-friendly format, often through an online portal. This is a digestible overview derived from a much more complex raw data file, which contains the information on all the individual SNPs tested.
Health-related findings are framed in terms of relative risk. For instance, a report might state you have a ‘slightly increased risk’ for a condition compared to the general population. This comparison is important for keeping the results in perspective, as it does not define your absolute risk.
SNP test results are probabilistic, not deterministic. A risk-associated SNP does not guarantee you will develop a condition, as lifestyle and environment are also major factors. Discussing concerning findings with a healthcare professional or genetic counselor can help translate the data into meaningful advice.
How SNP Testing Compares to Other Genetic Tests
To understand SNP testing, it helps to compare it with other methods like Whole Exome Sequencing (WES) and Whole Genome Sequencing (WGS). If the genome is an encyclopedia, SNP testing is like checking specific, pre-selected letters known to vary among people.
Whole Exome Sequencing (WES) reads the ‘exome,’ which includes all protein-coding regions of your genes. In the encyclopedia analogy, this is like reading the main paragraphs of every chapter. The exome is only 1-2% of the genome but contains most known disease-causing mutations.
Whole Genome Sequencing (WGS) is the most comprehensive approach, akin to reading the entire encyclopedia from cover to cover. WGS captures information on nearly all of your DNA, including the exome and non-coding regions. This allows for the discovery of rare variants other tests would miss.
The trade-off between these methods is breadth versus cost. SNP testing is efficient and affordable for examining common variations. WES and WGS provide a much deeper view of your genetic information but are significantly more expensive and generate complex data requiring extensive analysis.