· Ann Wu, MD MPH · Genetics 101
Whole Exome Sequencing vs. Whole Genome Sequencing: What's the Difference—and Why It Matters
WES and WGS sound similar but differ in meaningful ways. Here's how they compare and why one may be recommended over the other for your child.
Advances in genetic technology are transforming pediatric care by giving families and clinicians powerful tools to better understand, diagnose, and treat rare and complex conditions. Two of the most important tools in this space are whole exome sequencing (WES) and whole genome sequencing (WGS).
They sound similar, but they differ in meaningful ways. Understanding those differences can help clarify why one approach may be recommended over the other for your child.
The basics: your child’s genetic blueprint
Every child’s body is guided by DNA—a complete set of genetic instructions known as the genome.
Within that genome:
- Only about 1–2% consists of genes that code for proteins
- These protein-coding regions are called the exome
- The remaining ~98% includes regulatory and non-coding regions that still play important roles
This distinction is what separates whole exome from whole genome sequencing. The exome is currently the most characterized and clinically actionable part of the genome.
What is whole exome sequencing (WES)?
Whole exome sequencing focuses specifically on the exome—the small portion of DNA that directly codes for proteins.
Why this matters:
- Most known disease-causing mutations are found in these coding regions
- WES captures the areas where we have the strongest clinical understanding
Key advantages:
- Efficient and cost-effective
- Highly effective for detecting increased risk for many genetic disorders
- Generates a manageable amount of data for interpretation
- Less expensive
Limitations:
- Misses changes in non-coding regions
- May not detect certain structural or complex variants
What is whole genome sequencing (WGS)?
Whole genome sequencing reads nearly all of your child’s DNA—both coding and non-coding regions.
Why this matters:
- Captures everything, including regions we’re still learning to interpret
- Can detect variants that WES might miss
Key advantages:
- Most comprehensive view of the genome
- Better detection of structural variants, insertions, deletions, and regulatory changes
- Increasingly valuable as scientific knowledge grows
Limitations:
- Higher cost
- More complex data to analyze and interpret
WGS is often used when:
- Families or pediatricians are concerned about a child’s symptoms
- A comprehensive, future-proof dataset is desired
- Other tests have not provided an answer
An analogy to a book
Think of your child’s genome as a book:
- Whole exome sequencing reads only the important chapters we already know how to interpret
- Whole genome sequencing reads the entire book, including footnotes and sections we’re still learning to understand. Even though the footnotes may not seem to provide direct content of the book, it often includes equally important information that affects your understanding of the book.
Both approaches are valuable—just in different ways.
Why this matters in pediatric care
For children with or without symptoms:
- Earlier knowledge can mean earlier interventions
- More precise diagnoses can guide treatment and care plans
- Comprehensive data can support long-term health insights
As sequencing technology continues to evolve, both WES and WGS are becoming essential tools in pediatric medicine.
This article is for informational purposes only and is not a substitute for professional medical advice. If you have concerns about your child’s health, speak with your pediatrician.