Duplicated IGS in 25S rDNA. (A) Deletion patterns of the 25S rDNA in the HBa007F24 clone. All IGS-insertion occurred at the same site, 1,388–1,641 bp of 25S rDNA sequence, losing 253 bp. Assuming that deletions were accumulated, the sequence of deletion events can be estimated to be IV→ V→ III from the deletion pattern. Numbers on shade box represent position of normal 25S rRNA gene. Position and length of deleted sites are indicated. (B) IGSs duplicated in 25S rDNA were compared with normal IGS of 25-18S rDNA. Two subrepeats were differently regulated: Type II subrepeats have been easily lost, but type I subrepeats were not.