Use in clinical context
This type of test sequences only the exons (the protein-coding regions) of the gene to identify variants that could be causing an individual’s symptoms. It is useful because most single gene conditions are the result of variants in the exon sequence, and introns (the non-protein-coding regions) are often very large.
Single gene sequencing is appropriate where a genetic condition can be caused by one of many variants within a gene. In this situation, it can be more appropriate to sequence the whole gene rather than test for each variant individually, as with targeted variant testing.
An example of the use of single gene sequencing is for babies that have been clinically diagnosed with phenylketonuria (PKU) through the newborn blood spot screening programme. They may undergo single gene sequencing to determine the casual variant.
There are more than 500 variants in the PAH gene that have been identified in people with PKU, and identifying the specific variant(s) allows other family members to be tested to see if they are carriers for the condition.
In addition, knowing the variant(s) can give an indication about the severity of symptoms and may, in the future, indicate whether particular treatments may be beneficial.