Consequences
of the Domestication of Man’s Best Friend, The Dog
Changes that have occurred in the dog’s genome, both
during the domestication process and later through breed creation
A doctors thesis of Susanne Björnerfeldt,
Uppsala University, Department of Evolution, Genomics and Systematics,
Evolutionary Biology
The dog was the first animal to be domesticated and the process
started at least 15 000 years ago. Today it is the most morphologically
diverse mammal, with a huge variation in size and shape. Dogs
have always been useful to humans in several ways, from being
a food source, hunting companion, guard, social companion and
lately also a model for scientific research.
This thesis
describes some of the changes that have occurred in the dog’s
genome, both during the domestication process and later through
breed creation. To give a more comprehensive view, three genetic
systems were studied: maternally inherited mitochondrial DNA,
paternally inherited Y chromosome and biparental autosomal chromosomes.
I also sequenced complete mitochondrial genomes to view the
effect new living conditions might have had on dogs’ genes
after domestication. Finally, knowledge of the genetic structure
in purebred dogs was used to test analytic methods usable in
other species or in natural populations where little information
is available.
The domestication
process appears to have caused a relaxation of the selective
constraint in the mitochondrial genome, leading to a faster
rate of accumulation of nonsynonymous changes in the mitochondrial
genes. Later, the process of breed creation resulted in genetically
separated breed groups. Breeds are a result from an unequal
contribution of males and females with only a few popular sires
contributing and a larger amount of dams. However, modern breeder
preferences might lead to disruptive selective forces within
breeds, which can result in additional fragmentation of breeds.
The increase in linkage disequilibrium that this represents
increases the value of purebred dogs as model organisms for
the identification and mapping of diseases and traits. Purebred
dogs’ potential for these kinds of studies will probably
increase the more we know about the dog’s genome.
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