Genomics
Whole Exome Sequencing
What an exome can find, what it routinely misses, and why a variant report needs clinical and family context.
What is sequenced
The exome focuses on protein-coding regions
Whole exome sequencing examines many exons—the portions of genes that contain instructions for proteins—and nearby splice regions. It can identify some coding-region variants across many genes at once, which can be helpful when more than one genetic explanation fits a well-defined clinical question.
It is not a uniform read of every base. Coverage limits and gaps occur, and standard exome methods may miss repeat expansions, structural changes, mitochondrial variants, low-level mosaicism, and variants in regulatory or other noncoding regions. Detection also varies by laboratory pipeline.
An exome is not a complete genetic or disease-risk answer. A broad dataset does not make every association clinically meaningful or every future outcome predictable.
Reading a report
Classification is the beginning of interpretation
Pathogenic or likely pathogenic variant
A laboratory may classify a variant as disease-associated, but the finding still needs to be matched to the gene, inheritance pattern, phenotype, family history, and quality of evidence.
Variant of uncertain significance
Variants of uncertain significance (VUS) do not have enough evidence for a confident benign or disease-associated classification. A VUS generally should not drive irreversible medical decisions.
Negative or uninformative result
No reportable variant does not exclude a genetic condition. The causal change may be outside the regions assessed, poorly covered, technically difficult to detect, or not yet understood.
Incidental or secondary finding
Testing can uncover information unrelated to the original question, including findings with implications for relatives. Preferences for receiving incidental findings should be discussed before analysis.
From variant to person
Penetrance and context change what a finding means
Penetrance describes how often people with a particular variant develop the associated trait or condition. It may be incomplete and can depend on age, sex, ancestry, environment, other genes, and how families were selected for study.
A result should therefore be considered alongside symptoms, examination, family history, and the reason testing began. Risk estimates derived from one population may not transfer cleanly to another.
A safer sequence
- Define the question. Decide whether the goal is diagnostic clarification, family planning, or another specific decision.
- Discuss consent. Consider privacy, family implications, and preferences around incidental findings before sequencing.
- Interpret with expertise. Genetic counseling can help connect laboratory classification, inheritance, penetrance, and personal context.
- Verify consequential findings. Confirmatory testing in an appropriate clinical laboratory may be needed before a result changes screening, treatment, or testing of relatives.
Related diagnostic guides
For non-genetic risk assessment, begin with a focused laboratory question. For modeled molecular signals rather than inherited variants, read the biological-age overview.