(This blog originally posted on 7/15/2005.)
It seems more and more that the portion of the purebred "show" dog world which preaches and practices genetic testing and culling based on genetic test results are heading down an increasingly narrow alley.
The path they espouse, that 'everything is genetic' and diseases in dogs can be cured simply by selecting against the genes that cause disease, is well, old school. It is a philosophy based on "Central Dogma". Central Dogma, according to Mae-Wan Ho (of ISIS), is the theory "of molecular biology [which] decrees that genetic information flows strictly one way, from DNA to RNA to protein, and by implication, to the characteristic determined by that protein."
The thing is this approach to genetics and the relationship between genes and disease has no room for acknowledgement of environmental influences. Thusly, dogs still get Hip Dysplasia despite decades of selection against the "HD genes".
Here are some highlights from the article: GENETIC DETERMINISM AS A FAILING PARADIGM IN BIOLOGY AND MEDICINE: Implications for Health and Wellness, by Richard C. Strohman, University of California, Berkeley
"The major new idea here is that these levels of control are not reducibly connected; it is not possible, for example, to reduce common cancer to rules that govern DNA, just as it is not possible to reduce intelligence simply to the laws governing ion fluxes in brain neurons. DNA is involved in the phenotype "cancer" or "intelligence," but the cause of both lies elsewhere at higher levels of organization, including the level of the cell as a whole and the level of cell-cell networking.
This short answer is already extremely complex compared to the idea of reducibility, that ultimate control is in the gene"
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"We are becoming aware of theories of development that do not rely so heavily on genetic mutation as the source of new morphology and action but that instead emphasize the presence of robust generic processes of cells and organisms that generate new phenotypes."
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"What used to be referred to as the book of life written in the concrete of DNA is now being referred to as the flexible genome. Genes alone are vitally important; they are necessary but not sufficient to determine function or dysfunction in cells and organisms (the exceptions are the rare monogenic diseases discussed here). "
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"Second, real genetic diseases are rare and account for less than 2% of the disease load in the economically advanced sectors of the postindustrial world. Common diseases like most cancer and cardiovascular diseases that account for over 70% of premature morbidity and mortality are not genetic in the strict Mendelian sense. Nevertheless, the vast majority of our research budget is assigned to genetic-related problems. This 70% represents multifactorial diseases involving many genes whose interactions with one another and with their encoded proteins define an open network sensitive to environmental signals.1,15 The problem here is that, while the HGP [Human Genome Project] will be able to provide a detailed genetic map for complex polygenic diseases, it cannot provide the instructions for reading these maps. Therefore, insights into the vast majority of complex human diseases and into their prevention are not to be expected from the HGP as such. Third, therefore, multifactorial diseases and states of health and wellness are to be seen as emergent features of these interactive informational networks. They are not reducible solely to the actions of single or even multiple genetic agents or to the actions of their encoded proteins."
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"Concepts of health and wellness are characteristics of whole organisms and of processes that are time and place dependent-dynamic processes open to environmental signals and contextualized by an individual's life experience."
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"Here the focus is on redundant genes that more than one gene may specify any given function. In this case the reductionistic plan to associate genetic causality with complex phenotype is brought into question since the major research approach, saturation mutagenesis, depends completely on the uniqueness equation. This approach to understanding disease will generate a map or network of factors that interact to provide a useful background for a complex phenotype. However, as argued here, ultimate behavior is encoded not in DNA but rather in the environmentally interactive cellular epigenetic network, which includes the genome."
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"It is as if the cell has interposed between its genome and its behavior a second informational system able to integrate environmental and genetic information into its dynamical process and able to generate from this integration responses that are functional, or adaptive.
Genetic pathways specify organismal function only in rare cases, as in monogenic diseases like sickle cell anemia or muscular dystrophy, where mutation produces dysfunction in a protein of crucial importance."
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"The basic assumption is that complex disease states, at a cellular level, involve heritable changes that may include gene mutation but that also include persistent cytoplasmic changes. In addition, it must be clear what classical developmental biologists mean when they discuss complex phenotypes in terms of genotypes. What is usually meant is that all complex traits (e.g., intelligence, aggressiveness, and cancer) have some genetic basis. But this basis is so polygenic (interactive and epigenetic)-it may extend to the entire genome-that there is little in the way of practical meaning given to "genetic basis." For example, there is a genetic basis for speaking French, but the meaning of this does not go beyond the idea that there is a genetic basis for being human. In order to speak any language, we need to have something called a human genome (of which there are as many different kinds as there are humans) consisting of about 100,000 genes. But while these genes are necessary for speaking French, they are not sufficient. We also need the appropriate environment, the appropriate body, and the appropriate experience, all of which provide information not contained in the genome."
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"Diseases may be distributed according to whether they are determined before or after fertilization.36,37 Those determined before fertilization (2%) are, of course, genetic and are mostly not preventable. Of those determined after fertilization (98%), there may be multiple causality, including early developmental effects, but in theory at least these are all preventable."
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"The problem for medical genetic theory is that the common diseases of cancer and of the circulatory system appear to be new; they were not significant causes of death and disability in the early part of the 20th century.37 They are now the major cause of premature death and suffering in the industrial world. Clearly, this sudden shift in causality cannot be based on genetic change. Evolutionary theory and molecular biology agree completely that genetic adaptation due to mutation would take thousands of years and that change due to genetic recombination would also require much more time than the mere 50 to 100 years involved."
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And, there's a lot more great information in this article. Take some time to read the full text. It's long, but you don't have to be a scientist to understand it, or to see it's implications for dogs.
Do yourself another favor and search for "fluid genome" on the internet. The information you get may permanently change your way of thinking about genetics.
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