Genetics and Genomics in Racing: Speed Isn
Testing mares and stallions can help ensure foals are born free or at low risk of some genetic diseases. | iStock
Genetics refers to the study of genes and the way traits of conditions are passed down from one generation to another. Genomics, on the other hand, describes the study of all genes (the genome) including interactions of genes with each other and the environment. Although much of the genetic and genomic research done in Thoroughbreds is applied to racing performance, the full breadth of application of genetic and genomic research goes beyond that of faster horses.

Genetics and genomics allow for a more complete understanding of both simple and complex diseases. From a genetic perspective, “simple” is a term used to describe a disease that follows a single gene pattern of inheritance. These diseases are controlled by one gene, with other genes and outside factors having very little influence (i.e., the presence of the gene = disease). Diseases inherited this way are typically qualitative, where an animal either has the disease or it doesn’t (i.e., lethal white foal syndrome).

Complex diseases, on the other hand, are usually controlled by not one, but many different genes and are often affected by environmental factors, such as nutrition and living conditions (e.g., cervical vertebral stenotic myelopathy, or wobbler syndrome). This combination of both genetic and environmental factors results in complex or “multifactorial” diseases. Basically, three different scenarios determine the manifestation of a complex disease:

  • No genetic predisposition + environmental triggers = no clinical signs of disease;
  • Genetic predisposition + no environmental triggers = no clinical signs of disease; or
  • Genetic predisposition + environmental triggers = highly varied clinical signs of disease.

As a result, complex genetic diseases can be extremely difficult to diagnose early and/or prevent using tradition methods such as pedigree analyses and veterinary evaluations. In some instances, a simple disease might even be classified as complex based on the inability of epidemiological studies and pedigree analyses to find common factors among cases

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