What is a Linkage Test?

The vast majority of Embark genetic results are mutation tests, where probes are designed to determine the genotype of the exact disease-causing or trait-causing mutation. However, in cases where it is difficult to identify the exact gene causing a condition/appearance, scientists may be able to find sections of DNA that are usually inherited alongside the unknown gene, and perform a linkage test. 

DNA behaves in such a way that we can test sets of markers around these mutations and use that information to infer a genotype that we cannot assay directly. Because these mutations are physically linked to one another, we can use models to indirectly test for those mutations that we cannot directly assay.

One way to imagine the Linkage Test process is to picture a dog. If you see a Golden Retriever's head and tail, you can infer what the body is going to look like even though you can't see it. Because there is an element of randomness to how DNA gets shuffled around during mating, there are rare cases where the dog's body won't match expectations, but almost always, you can successfully predict the body type even if you can not see it directly. Our linkage tests work the same way.

Embark’s linkage tests are typically 98% predictive of true genotype, and linkage tests are identified in results for full transparency to our customers when this method is used on a particular test. Examples of linkage tests offered by Embark include Intervertebral Disc Disease (Type I) Risk, Blue Eye Color, and Furnishings.