Genetic Diagnosis by Whole Exome Sequencing

The emergence of new next-generation sequencing technologies has allowed us to make the high-quality complete sequencing of the exome available to the public in the past years.

When sequencing the exome, we are determining the exact sequences of the DNA in all the coding regions (which results in proteins) of the patient’s genome. Therefore, even though the exome approximately represents only 1% of the genome, it approximately contains 85% of the mutations that cause the disease.

Bioarray works with the Ion AmpliSeq™ system that provides the highest enrichment efficiency, offering 90% of uniformity in the coverage and with a large part of the nucleotides sequenced to a depth of around 20X. Bioarray also offers a complete bioinformatic study of the sequencing result, reporting in detail the found variants and the probability of the clinical meaning according to the background research of literature and existing data bases.

Genetic diagnosis by means of exome.

Exome sequencing can help to identify variants that can potentially cause the illness, in complex cases or in a rare case. This test allows the identification of variants of a single nucleotide (SNVs), small insertions or deletions and de novo mutations that can explain the inheritability of rare diseases. 

Normally, the exome sequencing is carried out when other tests, such as conventional laboratory tests or individual gene sequencing has not achieved a diagnosis.

Generally, the exome is recommended as a test previous to sequencing specific genes, when these have a low probability of causing the disease or when there is no clear clinical suspicion. In this sense, recent publications reveal the association of de novo mutations by exome sequencing with autism and other pathological conditions. On the contrary, in the presence of a clearer clinical hypothesis or with a higher probability, the sequencing of the gene or panel of genes under suspicion would be the first option.

On the other hand, it is important to understand that, when examining the complete exome of the individual, this test can give us further information on the medical status of the patient than what is originally being tested for, in other words, additional discoveries to the initial main reason for taking the test. Therefore, the evaluation of the results by a doctor or geneticist is essential.