These variants are filtered and reviewed by a genome analyst to identify 1 or more that might be causal for the observed clinical presentation. Variants (differences) from that reference are annotated using sophisticated bioinformatics tools and large-scale databases of genomic variation.
The average number of reads covering a given genomic position (the “read depth”) is typically 30–40. DNA is fragmented into small pieces and run on a high-throughput sequencing machine to generate millions of “nucleotide reads.” Reads are aligned to a reference genome, like puzzle pieces being assembled by looking at the image pictured on the box. Samples from biological parents are often sequenced at the same time to give additional context regarding inheritance. After appropriate pretest counselling, including review of possible results, a DNA sample is obtained from the patient, usually via a blood draw. Note: Variants in the KDM6A gene are linked to Kabuki syndrome. Middle panel was adapted from “Whole Genome Sequencing” by (2021) retrieved from. 5 Starting in 2021, genome sequencing is being performed as a clinical genetic test in Ontario, Canada. 3, 4 Genome sequencing is being integrated into health care systems internationally, most notably in the United Kingdom. 1 – 3 Sequencing an entire human genome (about 3.2 billion nucleotides) is now possible to complete in days to weeks, and at a similar cost to some advanced imaging tests or to a brief admission to hospital.
Genetic testing of patient constitutional DNA (i.e., their genome) is increasingly performed in medical practice. Test indications include suspected genetic disorders in children and adults for whom a targeted genetic testing approach is likely to be low yield or has already failed.Īnalytic validity, diagnostic yield and clinical utility are similar or superior to other clinical genetic tests, such as exome sequencing, chromosomal microarray analysis and next-generation sequencing gene panel tests.Īppropriate adoption of genome sequencing as a molecular diagnostic test in Canada would be facilitated by a cohesive national strategy for genomic medicine. Genome sequencing is a comprehensive genetic test that is being integrated into health care systems internationally.
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