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Genetic Testing

Although genetic testing can be very helpful when diagnosing patients, it won’t always give us the answers we wish for. For example, having a positive result from genetic testing doesn't always mean you will develop a disease. On the other hand, a negative result doesn't mean that you don't have a certain disorder.

The patient may have mutations in more than one disease gene (oligogenic) and it can be confusing. There are also novel mutations which are of unknown significance. Also, mutations may not be found (somatic mosaicism).

TYPES OF GENETIC TESTING

Whole Genome Sequencing (WGS)

The genome, or genetic material, of an organism (bacteria, virus, potato, human) is made up of DNA. Each organism has a unique DNA sequence which is composed of bases (A, T, C, and G). If you know the sequence of the bases in an organism, you have identified its unique DNA fingerprint, or pattern. Determining the order of bases is called sequencing. Whole genome sequencing is a laboratory procedure that determines the order of bases in the genome of an organism in one process.

Watch a video on Whole Genome Sequencing from the University of Washington.

Exome sequencing

Exome-Sequencing is an attractive alternative to Whole Genome Sequencing. Exome-Sequencing is partial sequencing. It analyzes dozens or even hundreds of genes but not the entire genome. It is good for obtaining detailed data and can be used to precisely identify SNVs (single nucleotide variants), as well as de novo mutations associated with Mendelian (also called monogenic diseases, caused by mutations in one gene) and common diseases.

 

There are two types of reliable DNA sequencing technologies widely used today: Sanger Sequencing and Next-Generation Sequencing.

Watch this great informative video from The Hospital for Sick Children (SickKids) in Toronto, Canada. 

Panel Sequencing

Panel sequencing is more targeted and therefore, it is highly recommended for primary immunodeficiency and autoinflammatory diseases. It is also more cost effective than doing an Exome sequencing or WGS.

Watch this video on “Targeted Panels or Exome – Which is Right for Inherited Disease Research?”

 

References:

What are whole exome sequencing and whole genome sequencing? https://ghr.nlm.nih.gov/primer/testing/sequencing

Center for Disease Control and Prevention: https://www.cdc.gov/pulsenet/pathogens/wgs.html

Laboratories offering genetic testing