Brooks Equine Genetics Research Lab
Gait Study
Intro/Background
Have you ever wondered why gaited horses gait? Why some gaited horses can trot or pace and gait? What is it about the gaited breeds that makes them so unique?
The purpose of this study is to answer all of these questions! We will discover what makes a gaited horse gait by looking at the blueprint of life for all creatures: DNA. Horsemen have known for years that a trotting horse cannot be trained to gait; the only way to get a gaited horse is by breeding other gaited horses. There is something that gaited horses are inheriting from their parents – the genes to gait.
Genes are regions of DNA that code for a specific biological function or characteristic, such as hair color, blood type and number of fingers. Genes have different variants known as alleles; these are responsible for the differences we see among individuals. For example, everyone has the gene responsible for eye color, but some have the allele for blue eyes and others have the allele for brown eyes. The alleles have different sequences of nucleotides or bases, the basic building blocks of DNA. There are four bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Strung together in different combinations of a long chain, the bases provide the code for reading DNA and subsequently the genes.
Genes are packaged and stored together in chromosomes, which are stored in the nucleus of cells. All mammals have two copies of each chromosome, but the total number of chromosomes varies according to species. Humans have 46 chromosomes, horses have 64, donkeys have 62, and mules have 63. One copy of each chromosome is passed from each parent to the offspring; in the case of the mule, they inherit 32 chromosomes from the horse parent and 31 chromosomes from the donkey parent leading to the grand total of 63 chromosomes. One set of chromosomes, along with all the genes, is collectively known as the genome. In 2007, the horse genome was sequenced to reveal a 2.7-billion nucleotide long genome. With the genome sequenced, it is now possible to find genes and map them to a specific location on a chromosome.
Due to the complex nature of gait, we hypothesize that there are multiple genes involved with gait. Gait is influenced by the conformation and neurobiology of the horse, and to some extent, human intervention in the form of shoeing and training. Each of the physiological aspects are influenced by several other components. Conformation is impacted by bone length and thickness, muscle mass, and shoulder and hip angles. Nerve types, calcium and potassium concentrations, and synapse receptors and transmitters control the neurobiology. Several genes influence each of these components; therefore, it is unlikely that just one gene is responsible for gait, but rather a specific combination of genes and their alleles produce the various gaits.