Research Overview
Dawn Marshall
1) Gene discovery and the genetic basis of inherited disease in non-model organisms
This builds on previous work identifying genes
linked to phenotypic traits in mammals, including the gene and
mutation associated with white coat colour in Kermode bears. The
focus on non-model organisms is a strategic one, because many
wild species are evolutionarily more closely related to humans
than are model organisms. As a consequence they share many
inherited diseases with similar genetic causes. A specific
example of this is the 
condition hereditary gingival fibromatosis which
presents in humans as an overgrowth of the gingival tissues
leading to functional and aesthetic difficulties. Silver foxes,
Vulpes vulpes, manifest a similar condition called
hereditary hyperplastic gingivitis (HHG). Research is currently underway to
discover the gene and mutation associated with HHG in foxes.
This project utilizes resources available from the human and dog
genome projects.
2) Evolutionary history of mutations and rates and patterns of DNA sequence evolution
I am also interested in the origins of mutations and the
historical and 
evolutionary factors such as natural selection or
founder events that explain their current frequency and
geographic distribution. For example, I am investigating the
evolutionary history of
LINCL (late infantile neuronal ceroid lipofuscinosis)
mutations in the founder population of Newfoundland, to
determine whether a founder event is necessary and/or sufficient
to explain the prevalence of this condition on the island, as
opposed to another explanation such as natural selection via
heterozygote advantage.
A related question is what factors determine rates
and patterns of DNA sequence variation in different genes and
genomes. How DNA variation is disseminated in the genome is
interesting in its own right, and understanding the factors
shaping such patterns is necessary when DNA polymorphisms are
used to infer the evolutionary history of organisms. In this
context, I compared rates and patterns of evolution of genes in
the mitochondrial genome of chaffinches, and
identified mutational hotspots in the control region
sequences of these birds. Along with colleagues, I found
evidence for recombination in the
chloroplast genome of lodgepole pine, a result which has
significant impact on how we interpret genetic variation in this
genome. And, as part of the fox gene discovery project,
B.Sc. Honours student Sara Tully is conducting a molecular
evolutionary analysis of the SOS1 gene, a candidate gene for
hereditary hyperplastic gingivitis in silver foxes.
3) Phylogeography and evolutionary history of populations inferred using neutral genetic variation
Neutral polymorphisms in DNA 
allow us to delineate organismal history from the
level of the individual, family, and population (microevolution)
to species and higher taxa (macroevolution). I use DNA sequences
to investigate the historical demographics of populations and
subspecies of organisms such as Kermode bears,
chaffinches and
lodgepole
pine, focusing on factors like changes in population size,
range expansions, and ongoing gene flow. Phylogeography, the
study of the distribution of genetic lineages with respect to
geography, is a crucial aspect of this process. Understanding
population structure and history is vital to the conservation
and management of resource species. In this context, the phylogeographic origins of brook
trout (Salvelinus fontinalis) in southeastern
Labrador are being investigated in my laboratory in
collaboration with the Department of Environment and
Conservation Wildlife Division.
