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More on the evolution of dogs

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  • Steve Farmer
    Another new study on the domestication and genetics of dogs was published this morning in PLoS Biology, for those on the List following this issue: Canine
    Message 1 of 1 , Mar 2 9:51 AM
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      Another new study on the domestication and genetics of dogs was
      published this morning in PLoS Biology, for those on the List
      following this issue:

      Canine Morphology: Hunting for Genes and Tracking Mutations

      http://tinyurl.com/y9duoyf (open access).

      The paper covers major issues in studies of mutations that go far
      beyond the canine-domestication problem.

      Plain text of the summary and introduction only below.

      Steve

      *****


      Canine Morphology: Hunting for Genes and Tracking Mutation
      Abigail L. Shearin1,2, Elaine A. Ostrander1*

      1 National Human Genome Research Institute, National Institutes of
      Health, Bethesda, Maryland, United States of America, 2 University of
      Pennsylvania School of Veterinary Medicine, Philadelphia,
      Pennsylvania, United States of America
      Published: March 2, 2010

      Summary

      As a result of domestication, selection for desirable phenotypes, and
      breed propagation, the domestic dog is unmatched in its diversity as a
      land mammal. Exhibiting extraordinary levels of both interbreed
      heterogeneity and intrabreed homogeneity, evidenced in part by the
      extensive linkage disequilibrium observed in many breeds, the dog
      provides an as-yet unrealized opportunity to uncover the molecular
      mechanisms that govern natural variation across mammalian species. We
      herein discuss recent advances in canine genomics that have made
      exploration of genetic mechanisms controlling breed-specific
      differences possible. We consider some examples where molecular
      mechanisms controlling simple traits have been uncovered. Finally, we
      reveal how combinations of genes produce complex phenotypes that can
      be revealed through studies of dog breeds featuring specific traits.

      Introduction
      As Darwin himself noted, the domestic dog displays a remarkable level
      of phenotypic diversity [1], and it is arguably the most
      morphologically variable land mammal on the earth today. Dogs can be
      big or small, tall or short, and display extremes of variation in
      terms of coat color and texture, skull shape and size, leg length and
      width, and a host of other traits (Figure 1). How this variation
      developed and is maintained within breeds intrigues both scientists
      [2]–[5] and the lay public alike.

      There are over 300 dog breeds identified worldwide, with nearly 170
      recognized in the United States by the American Kennel Club (AKC) [6].
      All domestic dog breeds are members of the same species, Canis
      familiaris, and possess a 2.8 Gb genome featuring 38 autosomes and the
      sex chromosomes, similar in size to the 3 Gb human genome. Dogs of any
      breed can, for the most part, be crossed to produce fertile offspring.
      Breeds were developed largely during the Victorian era, with special
      selection for both morphologic traits based on size, proportion, coat,
      etc., as well as behavior. To be a registered member of a breed, both
      of a dog's parents have to be registered members of the same breed,
      and their parents in turn must be registered members of the breed.
      Thus, each breed is effectively a closed breeding population that
      offers many statistical advantages for doing genetics beyond what can
      be done in studies of human populations [7].

      In this essay we consider some of the features of the canine genome
      relevant for successful studies of selected traits. We discuss current
      hypotheses regarding the development and maintenance of genetic
      variation in dogs today. We consider examples in which identified
      genes account for unique, and sometimes complex, phenotypes. Finally,
      we consider the implications of these findings for studies of true
      complex traits, such as those associated with behavioral genetics.
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