It
is often difficult to visualize what microsatellite markers look like since they are
identified, reproduced and made visible only after a long series of complex laboratory
procedures producing DNA sequence patterns which most people do not understand. After
digital scanning the electrophoretic plates however, such patterns can be transformed by
software and displayed as an electropherogram.
In the following example, software displays
the microsatellite marker, shown as "Segment A". The marker shows a repeating
pattern of DNA sequences. These sequences may be composed of two, three, four, or five (or
more) nucleotides, in which case, the sequence patterns are referred to as di, tri, tetra,
or penta-nucleotides. Before and after the microsatellite segment, are
"flanking" sequences, which are important in the location of these
microsatellites. By "priming" the DNA segments (with commercially available
primers) for the flanking sequence before and after the microsatellite, we are able to
find that marker sequence in almost all shrimp samples belonging to the same species.
Good markers are those that show high
degrees of variability (within a marker locus) and those which occur across a wide range
of samplings reflective of the population bio-diversity. The electropherogram of many test
individuals are statistically compressed into an allele frequency chart as displayed
below, so that analysis may be made on the loci for use as markers when related to a
targeted purpose (as a relational marker, as a gene marker, or as a trait related marker).
The analysis process is a combination of software and scientific interpretation. The
resulting information is simplified for user understanding, and is usually in the form of
a list or table identifying specific animals displaying profiles indicative of
relatedness, tagging or trait targeting.  |
