Screening for del20q by real-time PCR. (A) The copy number of the L3MBTL gene was determined in DNA from purified peripheral blood granulocytes using 2 SYBR real-time PCR assays with primer pairs located in L3MBTL exon 2 (quadrangles) and exon 9 (circles). Samples with gene copy values less than a threshold of 1.8 in both assays are marked in red and identified by unique patient numbers. (B) Patients with decreased L3MBTL gene copy number were further examined with real-time PCR assays for the neighboring genes PTPRT and TOX2. The decreased copy number was confirmed in all cases. nd indicates not determined.