Annotation of the companion animal genomes and subsequent development of genomic tools has greatly facilitated the genetic research in dogs, cats and horses over the past five years. Advancement of modern technologies has expedited gene discovery and a growing number of new disease genes are being described every year. The gene discoveries have enabled the development of the genetic tests available today for both pet owners and breeders.  

The information delivered by gene tests can be leveraged in many ways: 

  • to diagnose different diseases (e.g. certain eye diseases)
  • to predict the disease risk based on the genotype 
  • to distinct carriers and non-carriers in the breed to enable smart breeding decisions and to eliminate genetic diseases
  • to keep healthy carriers in breeding programs to maintain genetic diversity within the breed
     

Optimised breeding and animal care

Breeding of purebred dogs has resulted in the creation of over 400 breeds with enrichment of over 500 inherited disorders – breed-specific as well as across breeds, and often with a high frequency. 
A targeted DNA test of a specific disease discriminates genetically normal, carrier and affected dogs from each other and helps breeders optimise their breeding plans.
Many kennel clubs and breed associations have made DNA testing as an integral part of the breeding programmes as systematic assessment of especially genetic diversity helps breeders to monitor and reduce the incidence of the inherited diseases or even eradicate them from the populations while maintaining the necessary diversity for the breed to stay healthy.
For veterinarians the DNA test results serve as a diagnostic tool completing the view over animal health.
 

How a dog inherits its genes

A dog has 39 chromosome pairs including 38 autosomal chromosome pairs and sex chromosomes (X female, Y male). One of the chromosomes comes from the dam and one from the sire. The Y chromosome is always inherited from the sire, which determines the sex of the offspring. The genes exist in the DNA strand which is packed into the chromosomes.

The genes usually have many different alleles, which are alternate forms of the same genes differing from each other. Every dog has two alleles for each gene as inherited from the parents. When alleles of a given gene are copies of each other they are homozygous. If they differ from each other they are heterozygous. 

Genetic traits can be inherited in many ways. A common mode of inheritance in inbred populations is autosomal recessive, although some dominant and X-linked traits exist. These so called Mendelian traits cause usually single gene disorders. However, it is important to keep in mind that the penetration of the disease may vary and individuals with the same mutation may differ. Many common disorders are also polygenic being affected by several genes and environmental factors. Each genetic locus contributes to the disease risk and the disease outcome is defined by the combination of risk genes and environmental factors.