Two Ways to Read Your DNA
When people talk about "DNA testing," they're often referring to two fundamentally different technologies: genotyping and whole genome sequencing (WGS). Both read your genetic code, but they do so at very different levels of depth — and with very different implications for what you can learn.
As costs continue to fall and genomic science matures, understanding the distinction between these two approaches is increasingly relevant for consumers, patients, and researchers alike.
What Is Genotyping?
Genotyping doesn't read your entire genome. Instead, it scans a predefined set of specific locations in your DNA — typically hundreds of thousands of SNPs (Single Nucleotide Polymorphisms), which are positions where the DNA "letter" commonly varies between individuals.
Most consumer DNA tests (ancestry tests, trait tests, and many health tests) are genotyping-based. The technology used is called a SNP microarray or DNA chip — a tool that can simultaneously check many pre-selected positions across the genome.
Strengths of Genotyping
- Low cost — consumer tests typically range from modest to moderate pricing
- Fast turnaround — often results within a few weeks
- Well-suited for ancestry, relative matching, and common variant health screening
- Large databases for comparison (especially for ancestry purposes)
Limitations of Genotyping
- Only checks pre-selected positions — cannot detect rare or novel variants
- Misses structural variations, insertions, deletions, and copy number variants
- Cannot sequence regions not covered by the chip design
What Is Whole Genome Sequencing?
Whole genome sequencing reads every single base pair in your DNA — all approximately 3.2 billion of them. Rather than checking specific locations, WGS generates a complete readout of your genetic code from scratch.
Until recently, WGS was prohibitively expensive (the first human genome cost roughly $3 billion to sequence in 2003). Advances in sequencing technology have reduced this dramatically, and clinical WGS is now becoming more accessible.
Strengths of Whole Genome Sequencing
- Complete picture — detects virtually all genetic variation types
- Can identify rare variants, structural changes, and novel mutations
- Data can be reanalyzed as science advances without re-testing
- Gold standard for clinical diagnostics of rare and complex diseases
Limitations of Whole Genome Sequencing
- Higher cost than genotyping (though falling rapidly)
- Generates enormous amounts of data — requires significant computational analysis
- Many variants detected are variants of uncertain significance (VUS) — not yet understood
- Requires careful interpretation, ideally with a genetic counselor
Side-by-Side Comparison
| Feature | Genotyping | Whole Genome Sequencing |
|---|---|---|
| Coverage | ~0.02% of genome (selected SNPs) | ~100% of genome |
| Cost | Lower | Higher (decreasing) |
| Rare variant detection | Limited | Comprehensive |
| Best use case | Ancestry, common health variants | Clinical diagnosis, research |
| Data reanalysis | Limited | Yes — data can be queried again |
What Does the Future Look Like?
The cost of whole genome sequencing continues to drop. Some researchers and healthcare systems are already exploring whether population-level WGS could become part of routine preventive healthcare — flagging genetic risks before disease develops and enabling truly personalized medicine.
For now, genotyping remains the dominant consumer technology due to its cost and scalability. But as WGS becomes more affordable, the line between "consumer" and "clinical" DNA testing is likely to blur considerably over the next decade.
Which Should You Choose?
For most people curious about ancestry or common health variants, a genotyping-based consumer test is the practical and affordable starting point. If you're dealing with a suspected rare genetic condition, experiencing unexplained symptoms with a possible genetic component, or working with a specialist, clinical-grade whole genome sequencing — ordered and interpreted by a healthcare provider — is the more appropriate tool.