Whole-exome sequencing (WES) is helping physicians diagnose a genetic condition that has defied diagnosis by traditional means. The implication here is that exons in the nuclear genome are sequenced in the hopes that, by comparison with the genomes of nonaffected individuals, a diagnosis might be revealed.
If you were ordering WES for a patient, would you also include an analysis of the patient's mitochondrial genome?

Verified step by step guidance

1. Understand that Whole-exome sequencing (WES) targets the exons of nuclear DNA, which are the protein-coding regions of the nuclear genome.
2. Recognize that the mitochondrial genome is separate from the nuclear genome and consists of a small circular DNA molecule found in mitochondria, which is not covered by standard WES.
3. Consider that many genetic conditions can be caused by mutations in mitochondrial DNA, which would not be detected by WES alone.
4. Therefore, if a mitochondrial disorder is suspected or if the clinical presentation suggests mitochondrial involvement, it is important to order a separate analysis specifically targeting the mitochondrial genome.
5. In summary, WES does not include mitochondrial DNA analysis, so to comprehensively evaluate genetic causes, especially those related to mitochondria, a dedicated mitochondrial genome analysis should be included.

Key Concepts

Whole-Exome Sequencing (WES)

WES is a genomic technique that sequences all the protein-coding regions (exons) of nuclear DNA. Since exons represent about 1-2% of the genome but harbor most known disease-causing mutations, WES is efficient for identifying genetic variants linked to disorders. It focuses on nuclear DNA and typically excludes non-coding regions and mitochondrial DNA.

Mitochondrial Genome and Its Role in Disease

The mitochondrial genome is a small, circular DNA molecule found in mitochondria, inherited maternally and separate from nuclear DNA. Mutations in mitochondrial DNA can cause distinct genetic disorders, often affecting energy metabolism. Because WES targets nuclear exons, mitochondrial DNA is usually not analyzed unless specifically requested.

Diagnostic Strategy for Genetic Disorders

Choosing which genomic regions to analyze depends on the suspected disease and inheritance pattern. For unexplained conditions, including mitochondrial genome analysis alongside WES can be crucial if mitochondrial disease is suspected. Comprehensive diagnosis may require combining nuclear and mitochondrial DNA sequencing to capture all possible genetic causes.