bawhitman
UKC Forum Member
Registered: Jul 2008
Location: NC
Posts: 73 |
Here comes more...
“If you use population genetics for your dogs, I certainly hope one man can live long enough to see it completed.”
Population genetics simply do not apply to selective breeding of highly specialized hounds. I have never made the claim that it does and in fact in response to your “Genetic Drift” post I clearly stated that genetic drift, a term you were using in describing selective breeding, is a population level phenomenon and not applicable to selective breeding.
I have already pointed out many of the weaknesses of the two references that you posted on the redbone board. I hardly have time to critique the others, but one thing I am sure of is that our understanding of genetics just since 2000 (your most recent published reference) and most certainly since 1950 is staggering. The older publications are quite questionable. After all, DNA’s role in heredity was not confirmed until 1952 by Alfred Hershey (Hershey A, and Chase M 1952. "Independent functions of viral protein and nucleic acid in growth of bacteriophage". Journal of General Physiology 36 (1): 39–56.) I am not saying that there is not useful information in the books you listed, but anyone can buy books off of Amazon, pick a few out of context tidbits from them and post the information as: 1) their own information, and 2) meaning something that the authors never intended.
I have a suggestion. How about you contact the authors of the above books and ask them make a post, to summarize their years of experience and knowledge and to impart some of their wisdom on us?
“You can carry the genetics to virtual theory if you want, but I am just trying to get some better breeding stock. Genetics has many loop holes. It is a young science, but I believe very helpful to breeders. I am aware that me, nor you, or anyone else can number polygenes as it affects dogs. The truth is when single gene theory does not behave as one individual gene, it is just thrown on the POLY stack for future study. No where in my post do I attempt to number polygenes, wisdom also tells me that you can't number them either.”
I am making no attempt to “carry genetics to virtual theory.” You made the claim that you can breed out a polygene fault in six generation in your post. A statement like that is “virtual theory,” whatever that means. You cannot assert that claim based on the information that we know about dogs or genetics. If you have a trait that is linked to 12 genes with 3-10 polymorphs each on 7 different chromosomes you sure as hell are not going to change it in any discernable way in six generations. Conversely, if you have a trait that is governed by 2 genes with two polymorphs all on the same chromosome it will not take 6 generations to change. Making the claim that it will take anyone, as a breeder, 6 generations of breeding to get rid of their dog’s flat feet or short ears is just NOT true! One cannot predict the number of generations it would take based on the current understanding of the canine genome.
“Concerning the tree traits. A true signature of a recessive is skipping generations only to reappear in future generations. Dominates bred out are never again seen because they are just that, they are bred out. I would ask you, what do you use to get treeing in your dogs? Test mating will show the treeing quality of the mating involved. Do you test mate? Why then do you question selection and test mating if you are breeding good dogs that look and tree properly?”
Here is where your knowledge of simple Medelian genetics is lacking. The whole basis of dominant and recessive genes is a numbers game. The numbers are plain and simple and depend on the initial frequency of the dominant and recessive alleles in the breeding pair, nothing more, and nothing less. If you breed two individuals that each carry only one copy of a recessive allele (these are called heterozygotes) the predicted outcome is as such: 25% of the offspring will have two copies of the dominant allele (homozygous dominant), 50% will come out having a copy of each a dominant allele and a recessive allele (heterozygous), and 25% will come out with two copies of the recessive allele (homozygous recessive). The numbers fall out differently depending on the composition of dominant and recessive alleles in the initial pairing. Cross two individuals each with two dominant copies of the alleles and all you will get is offspring with dominant alleles; cross two individuals with all recessive alleles and that is what you get—all recessive alleles in the offspring. Cross an individual with one recessive allele and one dominant to one that has two dominate alleles and you end up with 50% of the offspring having two dominate alleles and 50% having one dominate allele and one recessive allele. And finally, cross an individual with two dominant alleles to one with two recessive alleles and you with get 100% of the offspring that have one dominant allele and one recessive allele.
These are the basics of genetics, and they only hold true for simplest of traits, traits like Mendel described in his seed coat color of peas. The problem is numbers of offspring needed to see the expected results. If you identified a trait that was governed by simple Mendelian genetics in a dog and bred two heterozygotes expecting to get keep only the homozygous recessive individual, you will not see this expected ratio in a litter of 3. The reason is simple. Twenty-five percent of 3 is a fraction and you cannot produce fractions of dogs. You might see it in a litter of 10, and it would certainly see the expected 25% homozygous recessive by the time you had 100 offspring from the same cross. You are correct that dominants bred out are not seen again, but the same holds true for recessives. They just hide better, but once bred out they, too, are gone. Your notion that “A true signature of a recessive is skipping generations only to reappear in future generations” is not the whole story. Recessives can “skip” generations IF you have a really small number of individuals in the generation. Recessive alleles do not disappear or reappear; they are simply masked by the presence of a dominant allele. It is only when an individual has two copies of a recessive allele that it shows in the phenotype.
The other aspect of that you are failing to acknowledge is that if treeing ability is recessive, dogs would come in two forms: those that tree because they have two copies of the recessive tree allele and those that don’t because they either have one or two copies of the dominant allele. This is simply not the case. Hounds vary from those that will not tree at all to those that will tree leaves. This, in itself, is all the evidence one needs to know that treeing is not regulated by one gene with two alleles—one dominant and one recessive.
“Have you witnessed your theories go hunting? Get on the wood? Have the coon? Does all your breeding practices produce 75% quality tree hounds? I have seen all the above. This is why I am so determined to accomplish it for my hunting stock.”
This section is, again, base on flawed logic. I am not basing my critique of your post on theories. I did not invent genetics, nor is the study of genetics theory, but I do know how they work. The coat color of a pea has been shown by years of research to be regulated by one gene with two alleles. The behavior of treeing raccoons has never and likely will never be shown to be regulated by one gene, not to mention the learning aspect associated with the process. Dogs of any breed don’t come out of their mommas tracking and treeing raccoons. However, I have seen dogs of all kinds of breeds tree their butts off and I am sure others can attest to this as well. It was not selectively bred into these other dogs, but they LEARNED by being out in the woods with dogs that were selectively bred for the trait or by being encouraged to do so. I know of a doberman pinscher that will track and tree with the best of our hounds. He is silent on track, but he will run it and tree ahead of many hounds. Should we introduce him into our breeding programs? Does he carry the recessive alleles to change the way our hounds tree? The point is that a behavior such as treeing is NOT governed by a single gene, and thinking about changing the performance of any organism one gene at a time is not going to work well.
I commend your desire to achieve high standards in your breeding program. If you know of someone that produces 75% tree hounds, if you have seen it with your own eyes, then play the numbers game, buy several dogs from them and cull the ones that don’t turn out. You will have a great foundation and all the hard work has been done. You don’t seem to be doing that. You are on the boards posting misinformation about a subject of which you don’t have a full understanding—genetics. That is not going to get you a great foundation stock and it is serving to propagate misunderstanding about how to use genetics to one’s advantage in their breeding programs.
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