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p53 polymorphism has been found at contaminated sites; its functional role has yet to be
explored (Marchand et al. 2010).
Studies of germinal mutations are of great interest in ecotoxicology because they are
heritable. Analysis of tandem repeat DNA loci (TRDL), which showed much higher rates
of mutation than unique sequence DNA, appeared promising. These TR sequences consist
of short repeat series of 2 to 100 bp, located in noncoding regions of the genome and called
minisatellites or microsatellites depending on their structure. They are generally GC-rich,
and constitute hotspots for mutations. Increased rates of TR mutation have been observed
in wildlife as a result of environmental exposure. Thus, the relationship between germline
TR instability and exposure to pollutants has been explored (Yauk 1998, 2006; Bouffler et
al. 2006).
Yauk and Quinn (1996) have used multilocus DNA fingerprinting methodology to
study mutations
in situ
in herring gulls (
Larus argentatus
) nesting in industrialized urban
sites (the Great Lakes in north America). They found the mutation rate in herring gulls
inhabiting a heavily industrialized urban harbor to be more than twice as high as at
three rural sites. Such lesions, which were transmitted to future generations (Yauk 1998),
could be important biomarkers for heritable genetic changes resulting from
in situ
expo-
sure to environmental genotoxins in a free-living vertebrate species. Yauk et al. (2000)
further studied germinal mutations in herring gulls and demonstrated the impact of
environmental pollutants. They reported that gulls nesting near integrated steel mills
showed significantly higher mutation rates than gulls from rural locations. Distance of
the nesting location of herring gulls from the steel industry's coking ovens was nega-
tively correlated with minisatellite mutation rate, demonstrating significant risk for
induced germline mutations in cities with steel operations. For review, please refer to
Yauk (2004, 2006). Mutations in minisatellites have also been widely studied in mam-
mals (Dubrova et al. 1993) and fish (the medaka
Oryzias latipes
) (Shimada and Shima
1998, 2004) after irradiation. The studies have shown that some mutations were transmis-
sible to following generations. Instability of minisatellites observed after exposure to
nongenotoxic agents raises the question of the influence of epigenetic events on genomic
functions.
Another fundamental question concerns the impact of mutations at the population level.
Bickham and Smolen (1994) have suggested that mutations can reduce survival and repro-
ductive capacities, which could lead to the extinction of a species. On the other hand,
mutations were also shown to be important for evolution and life on earth (Wurgler and
Kramers 1992). Only, neutral mutations or mutations that bring a selective advantage have
persisted, and adaptive mutations are necessary for individuals to cope with environmen-
tal changes (Foster 1998). For the time being, the consequences of
in situ
mutations are not
well understood and should be better studied. We hope that in coming years, more studies
will be launched to increase our understanding.
13.2.6 Biomolecular Techniques for Genomic and Transcriptomic Studies
Molecular biology techniques have been developed to detect an array of lesions such
as mutations, DNA breakages, and recombinations with potential consequences on the
genome and its activity. A very limited number of plants and non-mammalian animal spe-
cies have been fully sequenced. This significantly restricts the development of DNA and
RNA microarray techniques in ecotoxicology for genomic studies.
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