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9 Understanding Genetic Relationships among Purebred Dogs: The PhyDo Project

Heidi G. Parker, Nathan B. Sutter, Elaine A. Ostrander


With the recent availability of the dog genome sequence (see Chapter 11), there is growing recognition of the domestic dog’s importance as a system for identifying genes that control basic aspects of mammalian development. The growing popularity of the dog stems, in part, from its unique history and population structure. Centuries of intense selective breeding have produced more than 400 recognized breeds of dogs, whose members are characterized by dramatic differences in morphology, behavior, and disease susceptibility (Wayne and Ostrander 1999; Chase et al. 2002). Whereas the variation observed between breeds is optimal for studies of population structure, uniformity within breeds makes the dog ideal for identifying and mapping genes involved in complex traits, particularly those associated with disease susceptibility and progression (Ostrander and Giniger 1997; Galibert et al. 1998; Ostrander et al. 2000; Sutter and Ostrander 2004).

Key to our utilization of the canine system is a deeper understanding of how the 400 recognized breeds were created and how their morphological and behavioral features are selectively maintained. Ideally, such an understanding should derive not from historical lore, but from objective genetic analysis. In this chapter, we summarize recent findings about the population structure of the domestic dog, outline approaches for further elucidation of breed relationships, and describe how knowledge of population structure is a vital component in the search for the genetic variants that give rise to breed-specific morphology, behavior, and disease susceptibility.

According to fossil records, dogs and humans have coexisted for about 17,000...

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