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10. MARKER EFFICIENCY
alleles per a locus and gene diversities (Table 10.2). This argues for their further applications
every time when DNA analyses are troublesome, for exotic species, rich in compounds making
difficult DNA isolation or simple at the first stages of studies, at which the overall view is
important. For example, on the area of Poland, the moss, Pleurozium schreberi (Wachowiak-Zielinska
and Zielinski 1995; Zielinski and Wachowiak-Zielinska 1995) reproduces only
vegetatively. The isozyme analysis was made first to have an idea about its clonal structure.
These early results revealed the enormous genetic diversity at the enzymatic level, so the
studies were broaden to thousands of individuals and with such a big number they can only
be accomplished using protein electrophoresis. Another nice example involves Pellia species
that are difficult to separate based on morphology. The simple starch gel electrophoresis and
only one cheap enzymatic procedure, peroxidase staining enables unequivocally to identify
all taxa. From the other markers, it is worthy to note ISJs and RAPDs that produce results
nearly the same as enzymes. As for RAPDs, in spite of many objections found elsewhere
in the literature, if properly done, they do offer a quick way of screening potential molecular
markers from many loci. However, taking into account that DNA of high purity is needed and
the isolation can take from a day to few, none marker system can be compared with the enzymes
in respect to their simplicity and availability, with seconds to obtain extracts. Finally,
organelle markers are more useful for studying phylogeographic structure than for genetic
diversity itself. On the other hand transposons are invaluable if one is interested in the tempo
of microevolutionary processes and adaptations to changing environmental conditions. The
movement of transposons is between the first signs of speciation.
10.5. MOLECULAR MARKERS FOR GENOME MAPPING
The mapping studies are different from all the others in a sense that each gene with
known function is worthy to map. This is to say that it is necessary to make efforts to map
even a single enzyme. After all, each DNA marker is only a sequence with unknown function
and presumably, it represents a repetitive DNA. Notwithstanding the above prerequisite,
whether to use or not any marker category depends on goals of genome mapping. Whenever