Types of Genetic Tests
1. There are two types of genetic tests: 1)linkage tests: A linkage test consists
of a piece of DNA that does not code for a protein product, but resides on the chromosome
near the gene. The closer that this piece of DNA is to the gene the “tighter” the
linkage, and hence the test is more accurate. A good linkage test should be around
90-95%. If the linkage is poor, then the test is unreliable.
2): direct tests: A direct test when properly assessed in a pedigree study is 100%
accurate. This means that every time you detect this mutation the dog is affected,
and you can decipher as well from the pedigrees. This is why a pedigree study is
an absolute. This type of test looks for a specific change in a specific gene, and
not just a neighboring piece of DNA that may be close to the gene.
Chromosomes are not static. When paired, as they are they can exchange DNA in a
process called crossover. Linkage markers can jump to their partner, and therefore
this affects the results of the test. The closer that the marker is to the gene,
it is less likely that this will occur. This is because the linkage marker and mutated
gene will jump, or crossover together.