Page 52 - 7 July 2012

Cloning
And The MiToChondriAl
dnA
The use of the pedigree as a selection tool has
been around since the first breeder attempted to improve his animals by controlling their mat- ing. That first breeder started us down the right path to make the pedigree an important tool in helping us reach our goals as breeders.
By using the pedigree, the breeder is able to visualize what he is doing and how that path to breeding a horse is built on Mendelian genetics. Mendelian genetics is the use of homozygous, heterozygous, dominant and recessive genes, illustrated in Mendel’s famous scientific experi- ment with the peas.
By looking at the pedigree, we know when we’re inbreeding to increase prepotency or set type, or outcrossing to increase hybrid vigor to get the desired animal. The idea is to properly put the genes together to breed the best horse. The pedigree is one way for us to plan the mat- ing of our horses because we can’t read the genes, but we can read who the individuals were in the pedigree that carried the desired genes.
Over the years the pedigrees of some indi- viduals have come under fire for being false. They were false for a number of reasons includ- ing the common practice of changing the name and pedigree of a good racehorse in hopes of finding a good match race for the horse. No one believes that this was right, but a look at the history of the breed shows that it was a common practice. They just did it.
When the American Quarter Horse became an official breed, this type of activity became
a problem for the American Quarter Horse
A closer look at the genetics and science behind cloning. by Larry Thornton
52 SPEEDHORSE, July 6, 2012
Association. It compromised the integrity of the breed, and that was against the rules set down by the founders of AQHA. With the advent of modern genetics and DNA testing we have moved to eliminate those kinds of problems, allowing us to hold true the integrity of the breed.
Horse Genome Project
I have always professed that the pedigree is just like a book—you have to open it and read it to get the full benefit of what is inside. When, in 2007, a team of geneticists announced they had sequenced the genome of the horse (his genetic makeup), it was as if they had opened the book and were about to start reading the genes. This on-going sequencing is allowing modern science to move forward in the genetic research that will eventually not only improve the health and well being of our modern horses, but also help us breed a better horse.
Since 2007, we have seen the introduction of several new genetic terms through the identi- fication of genes that contribute to the makeup of the horse and his ability to perform. One
of the primary areas of study is the mitochon- dria and its role in developing the elite equine performer or racehorse.
The mitochondria are the cell’s source of energy, or where the energy for the cell is gener- ated to propel the horse to do what he is bred to do. The mitochondria are found inside the cell, but outside the nucleus. The genetic mecha- nism that controls or enables the mitochondria
to do its job is housed in the mitochondrial DNA (MtDNA). The MtDNA is made up of a small number of genes with a significant job to do. By learning how the MtDNA does its job we can breed a better horse.
Dr. Allan Davie, of Southern Cross University in Australia, is one of several researchers looking into the workings of the mitochondria and the elite performance horse. In an official news release announcing a new study that started in January 2010, Dr. Davie explained, “It is well-established that a high level of aerobic power (maximum oxygen consump- tion) provides the physiological foundation for elite racing performance in humans and horses.
“Large differences exist within the species in relation to this maximum oxygen consumption and its response to training. Maximum oxygen consumption is influenced by the mitochondria found within individual cells.”
Dr. Davie added, “The current understand- ing is that mitochondrial DNA is the only genetic material outside the nucleic DNA that is transferred exclusively from the mother to offspring in mammals.”
He went on, “Mitochondrial density and function regulate aerobic power. Therefore, the genotype of the mitochondria—genetic history— is one of the key factors that determine muscle utilization of oxygen and aerobic performance.”
Researchers at the Tianjin University of Sport and the Beijing Institute of Genomics have joined Davie in this endeavor. Both of these universities have been studying the role of