A Simple Tandem Repeat sequence of 11 nucleotides has been found in the ITS
1 region of the rDNA of members of Order Xylariales. The number of repetiti
ons detected ranged from one to six, and they could be found in pure tandem
or interspersed. The same core sequences have also been found in DNA from
other organisms, although usually not repeated in tandem. These repetitions
could have been generated by slipped strand mispairing. The presence of th
is sequence increases the normal rate of divergence in the ITS1 of the Xyla
riales. The phylogenetic implications of the presence of this sequence in t
he molecular taxonomy of Xylariales are also discussed.