chevron_rightWhole-exome sequencing is a widely used next-generation sequencing (NGS) method that involves sequencing the protein-coding regions of the genome.
chevron_rightThe human exome represents less than 2% of the genome, but contains ~85% of known disease-related variants, making this method a cost-effective alternative to whole-genome sequencing.
chevron_rightIt consists of two steps: the first step is to select only the subset of DNA that encodes proteins. These regions are known as exons humans have about 180,000 exons, constituting about 1% of the human genome, or approximately 30 million base pairs.
chevron_rightThe second step is to sequence the exonic DNA using any high- throughput DNA sequencing technology.
chevron_rightPatient with undiagnosed genetic disease.
chevron_rightPatients presenting with Heterogeneous phenotypes.
chevron_rightpatient with family history of genetic syndromes
chevron_rightWES is most suitable for individuals witht.
chevron_rightA complex, unspecific genetic disorder with multiple differential diagnoses.
chevron_rightA genetically heterogeneous disorder
chevron_rightA suspected genetic disorder where a specific genetic test is not available Unsuccessful previous genetic testing.
Sample Requirement
chevron_rightWhole Blood: 2-4ml (4ml preferred) of whole blood in EDTA.
Methodology
chevron_rightNext-generation Sequencing using genomic DNA extracted from blood, the coding regions of all the genes are captured and sequenced simultaneously by NGS technology on an Illumina platform.
chevron_rightThe sequence data that is generated is aligned and analyzed for sequence variants.
Advantages
chevron_rightIdentifies variants across a wide range of applications.
chevron_rightAchieves comprehensive coverage of coding regions.
chevron_rightProvides a cost-effective alternative to whole-genome sequencing (4–5 Gb of sequencing per exome compared to ~90 Gb per whole human genome).
chevron_rightProduces a smaller, more manageable data set for faster, easier data analysis compared to whole-genome approaches.
Limitations
chevron_rightExome sequencing does not target 100% of the genes in the human genome; approximately 97% of exons are targeted.
chevron_rightHowever, ~10% of exons may not be covered at sufficient levels to reliably call heterozygous variants.
chevron_rightWES is not validated for the detection of structural variations (SVs), including copy number variants (CNVs), inversions, and translocations.
chevron_rightWES does not include the sequencing of non-coding intron regions.