Two approaches to reading your DNA
When a healthcare professional orders an NGS-based genetic study, the two main options are whole-genome sequencing (WGS) and exome sequencing (WES). Both are powerful tools, but they answer different questions. In this article we explain the differences so you can make the best decision.
What does each sequence?
- Exome (WES) — sequences the genome’s coding regions, i.e. the exons of the ~20,000 genes. This represents about 1-2% of total DNA, but contains around 85% of known disease-causing genetic variants.
- Whole genome (WGS) — sequences all 3.2 billion base pairs, including exons, introns, regulatory regions, intergenic DNA and mitochondrial DNA.
Strengths and limitations of each approach
Clinical exome
- Strengths: lower cost, faster analysis, very mature interpretation databases, ideal for Mendelian diseases.
- Limitations: misses non-coding variants, lower capacity to identify large structural variants (CNVs), and does not natively cover the mitochondrial genome.
Whole genome
- Strengths: uniform coverage without capture bias, detection of structural variants, CNVs and repeat expansions, access to regulatory and non-coding regions, reusable data as knowledge advances.
- Limitations: higher cost, much larger data volume, interpreting non-coding variants is still a challenge.
When to choose each?
Choose exome if:
- The clinical picture suggests a classic monogenic disease.
- There is a defined list of candidate genes.
- Budget is a determining factor.
- A fast diagnosis is needed in a specific clinical context.
Choose whole genome if:
- A previous exome was negative and non-coding or structural variants are sought.
- A structural variant, CNV or triplet expansion is suspected.
- A comprehensive analysis is desired that can be re-analysed in the future.
- The patient also wants pharmacogenomic, PRS and trait information in addition to clinical diagnosis.
Price context
The cost of the whole genome has fallen dramatically over the last decade. Today, the price difference between WES and WGS has narrowed significantly, making the whole genome an increasingly accessible option. At OmicaLabs we offer both services with competitive, transparent pricing.
Our services
At OmicaLabs we perform both whole-genome sequencing and clinical exome, always with advanced bioinformatic analysis and interpretation by genomics specialists. If you are unsure which option suits your case best, our team will be happy to advise you.