“one-eyed pinhead” has been identified. This condition is characterized by a single
eye and poor development in the head region. A disease with similar symptoms also
occurs in humans, but because so few examples can be found, fish are being used as
models for human beings in an example of analysis that is gaining major attention (Sakamoto et al. 1999).
Genetic analysis with DNA markers certainly provides an excellent approach to
marine organism breeding. Once a DNA marker map for the entire genome has
been completed, this method can be used in analyzing various useful genetic traits
in the same species.
This section explained about the need for marker use in selected marine
organism breeding, as well as an overview of its methods and the current state and
results of research in the field. A basic account of achievements already made in
human beings and other organisms was also provided. While the use of DNA
markers in selective breeding of marine organisms began relatively recently, the
achievements made with plants and livestock animals to date offer proof of its
efficacy (Williams et al. 1990).
5.8 Chapter Summary and Conclusion
Comparison of protein polymorphs and DNA polymorphs in terms of utility as
genetic markers for population analysis shows that isozymes are extremely
reliable in terms of accuracy of genetic identification and consistency of data.
While some sensitivity issues do exist, isozymes are highly useful in certain
instances.
D-loop region polymorphs from mitochondrial DNA are very diverse and
useful in determinations of genetic differentiation and relatedness in populations
and estimation of evolution times. Drawbacks include issues with the inbreeding
and increasing homozygosity rate characteristic of sexually reproducing populations and their inability to provide effective information in distinguishing
between simple mixing and genetic mixing within a population.
As explained previously, single gene loci from minisatellites and
microsatellites, which combine the excellent reproducibility and high sensitivity
of isozymes, are certain to play an important role in the future. Microsatellite DNA polymorphs in particular, which have a far greater number of usable
gene loci than minisatellite DNA polymorphs, are extremely useful and are
expected to serve as a source for new findings. Drawbacks to these VNTRs
include the complex and costly nature of the genetic polymorph detection
method, the relative scarcity of data to date, and the inability to compare findings
with those from other markers. Such issues are likely to be resolved at some
point as the approach is applied with new technology.
From a biodiversity preservation standpoint, the focus is on preserving local
populations and groups within a single species. Use of the latest DNA polymorph markers will allow detection and identification of hitherto unknown local
populations. Research management can be focused on populations as basic units
of reproduction. In terms of fish farming, these markers will need to be used in
5.7 New Marine Breeding with DNA Markers
141
eye and poor development in the head region. A disease with similar symptoms also
occurs in humans, but because so few examples can be found, fish are being used as
models for human beings in an example of analysis that is gaining major attention (Sakamoto et al. 1999).
Genetic analysis with DNA markers certainly provides an excellent approach to
marine organism breeding. Once a DNA marker map for the entire genome has
been completed, this method can be used in analyzing various useful genetic traits
in the same species.
This section explained about the need for marker use in selected marine
organism breeding, as well as an overview of its methods and the current state and
results of research in the field. A basic account of achievements already made in
human beings and other organisms was also provided. While the use of DNA
markers in selective breeding of marine organisms began relatively recently, the
achievements made with plants and livestock animals to date offer proof of its
efficacy (Williams et al. 1990).
5.8 Chapter Summary and Conclusion
Comparison of protein polymorphs and DNA polymorphs in terms of utility as
genetic markers for population analysis shows that isozymes are extremely
reliable in terms of accuracy of genetic identification and consistency of data.
While some sensitivity issues do exist, isozymes are highly useful in certain
instances.
D-loop region polymorphs from mitochondrial DNA are very diverse and
useful in determinations of genetic differentiation and relatedness in populations
and estimation of evolution times. Drawbacks include issues with the inbreeding
and increasing homozygosity rate characteristic of sexually reproducing populations and their inability to provide effective information in distinguishing
between simple mixing and genetic mixing within a population.
As explained previously, single gene loci from minisatellites and
microsatellites, which combine the excellent reproducibility and high sensitivity
of isozymes, are certain to play an important role in the future. Microsatellite DNA polymorphs in particular, which have a far greater number of usable
gene loci than minisatellite DNA polymorphs, are extremely useful and are
expected to serve as a source for new findings. Drawbacks to these VNTRs
include the complex and costly nature of the genetic polymorph detection
method, the relative scarcity of data to date, and the inability to compare findings
with those from other markers. Such issues are likely to be resolved at some
point as the approach is applied with new technology.
From a biodiversity preservation standpoint, the focus is on preserving local
populations and groups within a single species. Use of the latest DNA polymorph markers will allow detection and identification of hitherto unknown local
populations. Research management can be focused on populations as basic units
of reproduction. In terms of fish farming, these markers will need to be used in
5.7 New Marine Breeding with DNA Markers
141