Robert M. Purvis D.V.M.
The mystery of how traits are passed on is a wonder with a long history. It took some one with
the ability to observe what traits passed on and how they compared to the parents. In 1866, a monk, Gregor Mendel, noticed some traits that his garden produced, wrinkle seeds and flower color. At the time he did not know anything about genes and chromosomes, but his observations started a branch of science called Genetics.
My father was a dog trainer and breeder of Pointers and English Setters for a Southern
Plantation that kept about 50 dogs in their hunting string. Much like what all good dog breeders would do, he used the powers of observation to make decisions about which ones should mate. At that time, none of us have had the level of genetic knowledge that now is at everyone’s fingertips, available to improve the breeds we love so much. We would look at past generations of an animal to get an idea of what genetics had been passed along, the genotype, and what traits we observed or the way they looked, the phenotype.
So where do these traits come from and how are they passed on to the offspring? We now know
that chromosomes contain the genetic message about what traits are available, and the message they hold is contained in two strands of DNA or Deoxyribonucleic acid. I try to think of it as a string of pearls, where each individual pearl holds a message that may appear. These messages are contained in arrangements called genes. Originally, Mendel and Darwin, thought these messages of traits were in some part of the bloodstream. This is where the genetic term, “Half Blooded and Full Blooded” came from. They were trying to say, one gene was expressed but not the other counterpart. The tricky part for all of us as breeders of animals, is that the traits come from both the mother and the father making it very difficult to predict what the offspring will be like. As the cells divide to become an ova, or egg in the female and sperm in the male, only part of the genetic code is put into the egg or sperm. These cells that contain only half of the genetic code are called haploid cells. Mating allows the combination of two haploid cells, the sperm and the egg, to recombine and now grow cells that are call diploid cells. These
diploid cells have two chromosomes with a full set of genes just like the cells of the parents. One half came from the mother and the other part came from the father, and each of these halves contain genes that may be expressed as a trait or not. This recombination allows for endless possibilities of traits that can be expressed in the offspring for generations upon generations with very little possibility of repeating the exact same pattern.
Recently, genetic testing has allowed us to identify what messages some of the pearls contain
on the neckless and has helped to improve our ability to predict what the offspring of a mating may produce. Specific genes for diseases, hair color, body type, and even temperament are now closer to a breeder that ever before. It is a tool that helps predict traits that can result from a breeding by identifying specific genes that are involved in specific traits.
Will a breeder ever get to a point where the observations of a dog’s traits, and temperament as
well as body type can be thrown out as not important? I wish I could have my dad answer that question for all of us to laugh about an unexpected breeding in 1962. The Sire and the Dam were both what we called “Wash Outs”, meaning they hated the smell of quail, were afraid of horses, and loud gun noises made them very nervous. My duty after school was to go down to the kennel, check the dogs, an make sure everything was ok. When I walked into the lane which lead to a long row of individual kennels, I was surprised to see Jake and Mindy together, the “Wash Out Twins” and Jake was smoking a cigarette!
Sixty-three days later, Mindy delivered seven pups, that looked like a photo shoot for the cover of Field and Stream magazine. All seven pups were outstanding hunting dogs, and four of those pups won field trial championships over the next three years. “How could that happen I ask my Daddy?” His only reply was son, it is the wonder of genetics!