Simple Sequence Repeat (SSR)- a small segment of DNA, usually 2
to 5 bp in length that repeats itself a number of times. Useful
SSRs usually repeat the core motif 9-30 times. Some of the major
core motifs that we use in the development of SSR markers for
soybean include ATT, AT, CTT, and CT. Polymerase Chain Reaction
(PCR)- an in vitro method for producing the large amounts of a
specific fragment of DNA necessary for analysis. Basically a
reaction that Xeroxes DNA making millions of exact copies of the
same fragment. Step over here for more information about PCR.
SSR Marker Development The first step in the process of creating
a useful Simple Sequence Repeat (SSR) DNA marker is the
construction of a DNA library in which small pieces of soybean
DNA are inserted into a cloning vector. We use the older and
quite well-known soybean cultivar ‘Williams’ as the source of
soybean DNA for our DNA libraries. The cloning vector we use is
a plasmid vector, pBluescript +KS. Each individual plasmid,
containing a different