5.7.4 Analyzing Unknown Gene Loci Associated
with Beneficial Marine Fish Species
Fish in the salmon family have been the most closely analyzed of useful marine
species. As these species are also popular worldwide, they are expected to play a
leading role among fish species in the future (Limborg et al. 2012).
In rainbow trout, albinism is a dominant trait. (Albinism dominance is a rarity
among organisms in general.) The locus for the gene responsible for it (i.e., the
gene’s position) has been ascertained. This also means that a DNA marker has been
discovered to identify the location where the responsible gene is present. Among
quantitative traits that are difficult to analyze (i.e., traits for which the phenotype is
governed by a complex mixture of genes), gene loci associated with temperature
tolerance, spawning times, and resistance or sensitivity to infectious pancreatic
necrosis (IPN) have been found.
The achievement of these results is due in larger part to the creation of a (still
insufficient) genetic map for the rainbow trout. The finding demonstrates the
effectiveness of DNA markers and linkage analysis, and anticipation is growing for
selective breeding methods using DNA markers linked to useful traits. As more and
more DNA markers are stockpiled, analyses will focus on a greater number of
economically valuable traits, and DNA markers linked to those traits will soon be
discovered and used in selective breeding.
5.7.5 DNA Marker Identification of Gene Loci Associated
with Conditions in Human Beings and Other Animals
An almost uncountable range of diseases and conditions exist for which genes have
been isolated and identified in humans using DNA markers, including Duchenne
muscular dystrophy, familial adenomatous polyposis (FAP), Huntington’s chorea,
familiar Alzheimer’s disease, retinoblastoma, osteitis fibrosa cystica, viral tumors,
type 1 diabetes, ankylosing spondylitis, juvenile breast cancer, and obesity. Some
of these cannot be explained in terms of Mendelian inheritance or polygenic theory,
which has led to a constant stream of new findings (Andersson 2001).
Other organisms besides humans include livestock such as cattle, sheep, swine,
and chickens and grains such as rice and wheat, most of which have been subject to
genome analysis for industry or commercial purposes. Efforts are being made to use
as yet unknown genes governing economically valuable traits as information for
breeding.
Genes (including gene loci) have been specially identified for milk production
yields and milk fat quantity and meat quality (brisket) in cattle; for reduced fat (pork
acidification), non-elastic meat, E. coli resistance, number of vertebrae, and growth
in swine; for resistance to the Marek’s disease virus in chickens; and for rice blight
resistance and germination periods in rice.
Zebrafish have also been used in studied focused on hereditary diseases in
humans. In particular, a gene responsible for a hereditary disease known as
140
5 Genetic Diversity and DNA Markers in Fish
with Beneficial Marine Fish Species
Fish in the salmon family have been the most closely analyzed of useful marine
species. As these species are also popular worldwide, they are expected to play a
leading role among fish species in the future (Limborg et al. 2012).
In rainbow trout, albinism is a dominant trait. (Albinism dominance is a rarity
among organisms in general.) The locus for the gene responsible for it (i.e., the
gene’s position) has been ascertained. This also means that a DNA marker has been
discovered to identify the location where the responsible gene is present. Among
quantitative traits that are difficult to analyze (i.e., traits for which the phenotype is
governed by a complex mixture of genes), gene loci associated with temperature
tolerance, spawning times, and resistance or sensitivity to infectious pancreatic
necrosis (IPN) have been found.
The achievement of these results is due in larger part to the creation of a (still
insufficient) genetic map for the rainbow trout. The finding demonstrates the
effectiveness of DNA markers and linkage analysis, and anticipation is growing for
selective breeding methods using DNA markers linked to useful traits. As more and
more DNA markers are stockpiled, analyses will focus on a greater number of
economically valuable traits, and DNA markers linked to those traits will soon be
discovered and used in selective breeding.
5.7.5 DNA Marker Identification of Gene Loci Associated
with Conditions in Human Beings and Other Animals
An almost uncountable range of diseases and conditions exist for which genes have
been isolated and identified in humans using DNA markers, including Duchenne
muscular dystrophy, familial adenomatous polyposis (FAP), Huntington’s chorea,
familiar Alzheimer’s disease, retinoblastoma, osteitis fibrosa cystica, viral tumors,
type 1 diabetes, ankylosing spondylitis, juvenile breast cancer, and obesity. Some
of these cannot be explained in terms of Mendelian inheritance or polygenic theory,
which has led to a constant stream of new findings (Andersson 2001).
Other organisms besides humans include livestock such as cattle, sheep, swine,
and chickens and grains such as rice and wheat, most of which have been subject to
genome analysis for industry or commercial purposes. Efforts are being made to use
as yet unknown genes governing economically valuable traits as information for
breeding.
Genes (including gene loci) have been specially identified for milk production
yields and milk fat quantity and meat quality (brisket) in cattle; for reduced fat (pork
acidification), non-elastic meat, E. coli resistance, number of vertebrae, and growth
in swine; for resistance to the Marek’s disease virus in chickens; and for rice blight
resistance and germination periods in rice.
Zebrafish have also been used in studied focused on hereditary diseases in
humans. In particular, a gene responsible for a hereditary disease known as
140
5 Genetic Diversity and DNA Markers in Fish