21del PCR results for all 21 members of PGG2. Wild type gene amplicon = 111 bp. 21del amplicon = 90 bp. Sample SAWC 3100 (F14) is negative for all PPE38-related PCRs suggesting complete deletion of this region [see additional file 2, S8]. In isolates that possess both a normal and a 21del gene copy an additional amplicon of approximately 100 bp is seen. This presumably represents a heteroduplex comprising both amplicons.