FEATURE ARTICLE
Genetics and the Shape of Dogs
Studying the new sequence of the canine genome shows how tiny genetic changes can create enormous variation within a single species
Elaine A. Ostrander
Remaining Selective
The advances of the past three years in canine genetics have been enormous. The dog genome has been mapped and sequenced. A host of disease loci have been mapped, and in many cases the underlying mutations identified. Our understanding of how dog breeds relate to one another is beginning to develop, and we have a fundamental understanding of the organization of the canine genome. The issue of complex traits is no longer off-limits. We have begun to understand the genetic portfolio that leads to variation in body size and shape, and even some performance-associated behaviors.
Certainly the next few years will bring an explosion of disease-gene mapping. The genetics of canine cancer, heart disease, hip dysplasia, vision and hearing anomalies have all been areas of intense study, and investigators working on these problems are poised to take advantage of the recent advances described here. Whole-genome association studies are likely to replace family-based linkage studies as a way of finding genes associated with not only disease susceptibility and progression, but morphology and behavior as well.
What will the companion-animal and scientific communities do with this new information? It is certainly hoped that the disease-gene mapping will lead to the production of genetic tests and more thoughtful breeding programs associated with healthier, more long-lived dogs. It will be easier to select for particular physical traits such as body size or coat color, not only because we understand the underlying genetic pathways, but because genetic tests are likely to be made available as quickly as results are published. Finally, canine geneticists will finally have a chance to develop an understanding of the genes that cause both breed-specific behaviors (why do pointers point and herders herd?).
What is far less clear is whether we will come to understand what makes the domestic dog unique to us among all the animals in the mammalian world. We have domesticated dogs to the point that they display loyalty, friendship and companionship. We seek their company and approval and bring them into our homes, often as equal members of our family. We rejoice in their victories and mourn their deaths, often as we celebrate or mourn our own children. Is the genetics that defines this relationship within the dog, within ourselves, or both? None of the studies proposed are likely to answer that question, and perhaps that is okay. The comparative-genome projects of humans and dogs were designed to bring about an understanding of our similarities and differences. Perhaps scientists will have to be satisfied to understand that much, and leave as a mystery the genetic basis of approval, adoration and loyalty. At least for me and my dog, it's enough.
SIDEBAR: Picturing Dog-Human Homology
Bibliography
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