Recently, it has been become possible to use DNA polymorph (possessing
multiple alleles) markers to detect and identify previously unknown local clades of
marine fish species. Since resource management focuses on local groups and clades,
genetic marker-based monitoring systems for these populations must be adjusted to
acquire parent species and produce and release seedlings.
In contrast with fishing, fish farming involves artificial management of organisms, with genetic improvements carried out as in agriculture to meet breeding
goals related to various producer or customer demands. Explication of the improved
varieties’ genetic characteristics and preservation and management of the new
varieties are important tasks for this field. When a new variety is developed, the
spatial, labor, and economic requirements for the line’s preservation and management increase, and costs may increase substantially. If mixed raising becomes
possible through the employment of genetic markers in these improved varieties
and lines, however, the maintenance costs and labor requirements for management
of the parents and preservation of the line may decrease significantly down the road.
5.3 What Are Genetic Markers?
Genetic markers refer to instances in which a gene’s phenotype can be easily
distinguished and used to identify organisms or cells possessing it. Genetic markers
may be used as probes to identify the nucleus, chromosomes, or a gene’s position.
They may be used as indicators in assessing the genetic diversity of a fish or
shellfish population that is the subject of attention, or in determining intraspecific
geographic groups. In other words, they allow for direct observation of genetic
information and estimation of genetic relationships between organisms.
Markers commonly used in population genetics include body color, shape,
special features, blood type, proteins (isozymes, etc.), and defined DNA regions. In
all cases, polymorphs are recognized as a result of alleles. Effectiveness as a marker
depends on the degree of diversity (Giblett 1969; Queller and Goodnight 1989;
Williams et al. 1990; Kidd 1993; Sunnucks 2000).
Isozyme polymorphs, which have come to assume an important role as DNA
markers over the years, exist within DNA’s structural domain. Because they perform functions for the organism, they are associated in many cases with single gene
loci; even when multiple gene loci exist, variability is somewhat lacking. For this
reason, there are limits to their applicability in detecting differences between local
populations shortly after isolation from their habitat environment. In population
genetics research, the amount of genetic information is determined by the quantity
and quality (sensitivity) of genetic markers. This has naturally led to a desire to
develop more sensitive markers than isozymes, and recent years have seen rapid
advancements in research using DNA base sequence polymorphs that include
regions exhibiting high variability.
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5 Genetic Diversity and DNA Markers in Fish
multiple alleles) markers to detect and identify previously unknown local clades of
marine fish species. Since resource management focuses on local groups and clades,
genetic marker-based monitoring systems for these populations must be adjusted to
acquire parent species and produce and release seedlings.
In contrast with fishing, fish farming involves artificial management of organisms, with genetic improvements carried out as in agriculture to meet breeding
goals related to various producer or customer demands. Explication of the improved
varieties’ genetic characteristics and preservation and management of the new
varieties are important tasks for this field. When a new variety is developed, the
spatial, labor, and economic requirements for the line’s preservation and management increase, and costs may increase substantially. If mixed raising becomes
possible through the employment of genetic markers in these improved varieties
and lines, however, the maintenance costs and labor requirements for management
of the parents and preservation of the line may decrease significantly down the road.
5.3 What Are Genetic Markers?
Genetic markers refer to instances in which a gene’s phenotype can be easily
distinguished and used to identify organisms or cells possessing it. Genetic markers
may be used as probes to identify the nucleus, chromosomes, or a gene’s position.
They may be used as indicators in assessing the genetic diversity of a fish or
shellfish population that is the subject of attention, or in determining intraspecific
geographic groups. In other words, they allow for direct observation of genetic
information and estimation of genetic relationships between organisms.
Markers commonly used in population genetics include body color, shape,
special features, blood type, proteins (isozymes, etc.), and defined DNA regions. In
all cases, polymorphs are recognized as a result of alleles. Effectiveness as a marker
depends on the degree of diversity (Giblett 1969; Queller and Goodnight 1989;
Williams et al. 1990; Kidd 1993; Sunnucks 2000).
Isozyme polymorphs, which have come to assume an important role as DNA
markers over the years, exist within DNA’s structural domain. Because they perform functions for the organism, they are associated in many cases with single gene
loci; even when multiple gene loci exist, variability is somewhat lacking. For this
reason, there are limits to their applicability in detecting differences between local
populations shortly after isolation from their habitat environment. In population
genetics research, the amount of genetic information is determined by the quantity
and quality (sensitivity) of genetic markers. This has naturally led to a desire to
develop more sensitive markers than isozymes, and recent years have seen rapid
advancements in research using DNA base sequence polymorphs that include
regions exhibiting high variability.
112
5 Genetic Diversity and DNA Markers in Fish