Page 53 - 7 July 2012

the mitochondria and MtDNA in the human athlete. The goal of this project is to improve not only equine training methods, but also selection methods to pick a horse that will per- form at an optimum level for a given distance in a race. They want to find the genetic link between genotype and the different types of athletic ability.
The function of the mitochondria in energy production of an individual comes into play when we address the controversial issue of cloning. According to the most popular definition being distributed today, cloning is the advanced technology that reproduces an individual that is genetically identical to the individual we want to duplicate.
The goal of the cloning is to duplicate a great individual. An owner may want to keep
a special animal in his life and not lose that individual to old age. He may want to extend the life of his stallion and reap the benefits of his strong genetics as a breeding animal. He may want to reproduce the performance capa- bility of an animal. No matter the reason, some people want to duplicate a special animal.
Cloning
Cloning has faced some challenges—both physical and ethical—that have made the technique a source of great controversy. Some of the obstacles are:
1. Different Shapes, Sizes and Color
Clones don’t always look exactly like the cloned animal. This is due to what geneticists call “random migration of pigment cells during growth.” These variations come up during embryonic development, causing differences in color and markings from the donor animal, or the animal that is being cloned, to the clone.
2. Short lives and Disease Problems
A review of literature on the cloning process has indicated some concerns about cloning that include premature death of clones and the over- all general health of the clones. Many of the concerns about early death or unhealthy lives came with the death of Dolly, the first cloned
sheep. She died when she and her mates in the barn were stricken with illness. The cattle and sheep breeds that have been cloned have shown health issues, and while this problem exists in horse clones, it doesn’t seem to be as big of an issue. Still, one report indicated that health wise, it was more difficult to raise a clone than an offspring that was conceived through nor- mal reproductive paths.
3. loss of genetic Diversity
A third concern is more ethical than physical. Many believe if we clone all the good horses, we will stop improving the breed.
The goal of every breeder is to breed a better horse than he started with, and that stops with the clone. The second part of this concern is the linebreeding and inbreeding we already see in the industry, and how cloning would contribute to the shrinking gene pool. With cloning, breeders could simply continue with what is successful and not strive to improve the breed through more genetic diversity. Genetic improvement through hybrid vigor is a key component of improving any breed. The final part of this concern comes from the fact that the cloned individual may be the carrier of genetic defect, and the use of the clone as
a breeding animal would spread this problem deeper into the breed.
Cloning, in general, is not a new practice, as the plant industry has a long history of cloning certain plants. My own experience finds my horticulture students growing about 500 poin- settias each year. We grow our poinsettias by buying rooted cuttings and raising them to sell at Christmas time. We start by transplanting those cuttings into 6-inch pots in August. Each rooted cutting is a clone to the parent plant from which the cutting was taken. Thus they are genetically identical. The use of rooted cut- tings is called asexual reproduction, or the use of plant parts to reproduce the next generation.
The plant breeder explains that we can do this because each cell in the plant has all the information we need to produce a new plant. The cutting carries that information on to the
next plant or generation, and nothing is left behind. Thus the plant is a perfect clone of the parent plant. The plant breeder has found that some plants reproduce better through asexual reproduction than using seed or sexual repro- duction (the fertilization of the egg by pollen.)
Through normal sexual reproduction in horses, the stallion provides the sperm and
the mare provides the egg. The sperm carries one-half (50%) the nuclear DNA that is found in the nucleus of the sperm cell. The mare pro- vides one-half (50%) the nuclear DNA that is found in the nucleus of the egg cell. The result- ing foal inherits its entire nuclear DNA (100%) from its parents, making that foal a unique individual. It is through sexual reproduction that we put individuals together that hopefully improves the next generation of horses.
The natural process of the stallion and mare mating and passing on their nuclear DNA
is supplemented by the mare passing on her MtDNA to the foal. This takes us to a fourth concern about cloning:
4. The role of the MtDnA and how this part of an individual’s genetic identity can be lost when we clone
The February 2009 issue of The American Quarter Horse Journal published an article entitled “Pure Genetics,” which gives a great explanation of the procedure used to clone animals. The pro- cess is called “somatic cell nuclear transfer” and was explained by the Journal in four steps:
1) The process begins by selecting the cell donor and an oocyte donor. The cell donor
is the animal that is going to be cloned. The oocyte donor is a mare that gives a mature oocyte (female egg cell) to be used to house the genetic information of the animal to be cloned.
2) The DNA of the mature ooycte is removed by a process called oocyte enucleation. This means that the technician will remove
the nuclear DNA from the donated oocyte. Nuclear DNA is where most of the genetic information for an individual is housed in the cell. Then the DNA from the animal to be cloned is transferred to the donated ooycte. This is nuclear DNA from a somatic cell or
SPEEDHORSE, July 6, 2012 53