Predicting risk before anything goes wrong
Predictive testing looks for a known risk variant in a healthy person — most often when something runs in the family. A woman with several relatives affected by breast and ovarian cancer might test for a BRCA1 variant. A positive result does not mean she has cancer or certainly will; it means her risk is meaningfully raised, which opens doors to earlier and more frequent screening, risk-reducing options, and informed planning. This is the difference between a predictive test (you feel well, you're estimating future risk) and a diagnostic one (you have a symptom now and want its cause).
A related and growing category is the popular direct-to-consumer test you order online. These can be fun and sometimes genuinely useful, but they often report a handful of single-nucleotide polymorphisms rather than a full clinical analysis. A reassuring DTC result does not rule a condition out, and an alarming one deserves confirmation by a clinical lab before anyone loses sleep.
Matching drugs to DNA, and repairing genes directly
Pharmacogenomics is one of the most immediately practical corners of medical genetics. People inherit different versions of the liver enzymes that process drugs, so the same dose can be too weak in one person and dangerously strong in another. Testing the relevant genes can guide a doctor to pick the right drug, or the right dose, the first time — fewer side effects, less trial and error. It is genetics quietly improving everyday prescriptions.
Gene therapy goes further still: instead of working around a faulty gene, it tries to correct the problem at the source — delivering a working copy of a gene, or editing the DNA in a patient's own cells. Once science fiction, it is now an approved treatment for several previously untreatable conditions, including certain inherited blindness and blood disorders. It is not a cure-all — it is complex, costly, and tailored to specific diseases — but it marks a genuine shift from managing genetic disease to repairing it.
When a test finds more than you asked for
The broader the test, the more likely it stumbles onto something unrelated to the original question. An incidental finding — sometimes called a secondary finding — is exactly that: you sequence a child's genes to explain a developmental problem and discover, unexpectedly, a hereditary cancer syndrome variant that also affects a parent. Such findings can be life-saving when they prompt prevention, or distressing when they reveal a risk no one was ready to hear. Because of this, modern testing handles them deliberately.
- Before testing, you discuss whether and which incidental findings you want reported — informed consent up front.
- Labs typically report only well-established, actionable findings — risks you can actually do something about.
- A genetic counselor helps interpret a surprise result and think through what it means for relatives who share the gene.