number of potential gene loci than minisatellite DNA polymorphs, is certain to
result in new information emerging (Taniguchi 1996).
5.6.2 Genetic Diversity and Population Structure in Wild
Populations
Genetic diversity: To date, DNA polymorph analysis has been carried out for the
full range of regions in many varieties of fish, including the herring, black bass,
trout, ayu, blue spotted snapper, and pacific yellowfin tuna, in accordance with
restriction enzyme fragment length polymorphism (RFLP). With the introduction of
PCR, however, recent RFLP analysis has been conducted for amplified
high-mutation DNA D-loop regions. Mutations are detected more clearly in these
DNA loop regions than in functional regions, with applications in population
analysis (Frankham 1996; Yuhiro 1997)
The high level of haplotype diversity in DNA D-loop regions is observable in
wild populations of red seabream. Twenty-seven varieties of haplotype have been
detected, resulting from combinations of five different RFLPs, with a very high
diversity level of 0.905. Wild species population structure analysis using DNA
haplotype polymorphs as genetic markers has also been conducted for other beneficial fish species besides red seabream (Tabata and Mizuta 1997).
Development of microsatellite DNA polymorph marker detection primers has
enabled detection of multiple gene loci in many wild fish species (Takagi et al.
1997). In terms of the diversity of microsatellite DNA gene loci, comparison of the
average number of alleles per gene locus (Fig. 5.8) and heterozygosity rate clearly
shows greater sensitivity as a molecular gene marker than the values of isoenzyme
markers (Fig. 5.9). With regard to genetic diversity in wild red seabream populations, those of the Northern Pacific have been found to exhibit higher values than
those of the Southern Pacific.
Genetic differentiation between wild populations: Given the great diversity of
microsatellite DNA markers, one may expect them to exhibit great sensitivity
(applicability) in analysis of population structure, including genetic differentiation
between local fish populations (Tabata and Mizuta 1997; Tabata et al. 1997).
Microsatellite DNA markers remain in the development stages technically, however, and examples of application are few and far between. Primers are required for
microsatellite DNA marker detection, and have already been developed for the
Japanese seabass, three-spined stickleback, rainbow trout, Atlantic salmon, and red
sea bream; among these, population analysis research has been carried out for the
Atlantic salmon, trout, and red seabream. Ongoing development and data analysis
are under way for important fishery and cultured fish species such as the ayu, carp,
black skipjack tuna, amberjack, and olive flounder.
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5 Genetic Diversity and DNA Markers in Fish
result in new information emerging (Taniguchi 1996).
5.6.2 Genetic Diversity and Population Structure in Wild
Populations
Genetic diversity: To date, DNA polymorph analysis has been carried out for the
full range of regions in many varieties of fish, including the herring, black bass,
trout, ayu, blue spotted snapper, and pacific yellowfin tuna, in accordance with
restriction enzyme fragment length polymorphism (RFLP). With the introduction of
PCR, however, recent RFLP analysis has been conducted for amplified
high-mutation DNA D-loop regions. Mutations are detected more clearly in these
DNA loop regions than in functional regions, with applications in population
analysis (Frankham 1996; Yuhiro 1997)
The high level of haplotype diversity in DNA D-loop regions is observable in
wild populations of red seabream. Twenty-seven varieties of haplotype have been
detected, resulting from combinations of five different RFLPs, with a very high
diversity level of 0.905. Wild species population structure analysis using DNA
haplotype polymorphs as genetic markers has also been conducted for other beneficial fish species besides red seabream (Tabata and Mizuta 1997).
Development of microsatellite DNA polymorph marker detection primers has
enabled detection of multiple gene loci in many wild fish species (Takagi et al.
1997). In terms of the diversity of microsatellite DNA gene loci, comparison of the
average number of alleles per gene locus (Fig. 5.8) and heterozygosity rate clearly
shows greater sensitivity as a molecular gene marker than the values of isoenzyme
markers (Fig. 5.9). With regard to genetic diversity in wild red seabream populations, those of the Northern Pacific have been found to exhibit higher values than
those of the Southern Pacific.
Genetic differentiation between wild populations: Given the great diversity of
microsatellite DNA markers, one may expect them to exhibit great sensitivity
(applicability) in analysis of population structure, including genetic differentiation
between local fish populations (Tabata and Mizuta 1997; Tabata et al. 1997).
Microsatellite DNA markers remain in the development stages technically, however, and examples of application are few and far between. Primers are required for
microsatellite DNA marker detection, and have already been developed for the
Japanese seabass, three-spined stickleback, rainbow trout, Atlantic salmon, and red
sea bream; among these, population analysis research has been carried out for the
Atlantic salmon, trout, and red seabream. Ongoing development and data analysis
are under way for important fishery and cultured fish species such as the ayu, carp,
black skipjack tuna, amberjack, and olive flounder.
126
5 Genetic Diversity and DNA Markers in Fish