False positive event calls could be due to high GC content. A 5.5 kb variable region (chr25:28829889-28835660) was identified in one control self to self array CGH. GC Percent in 5-Base Windows, Array CGH probe, Gap, RefSeq Gene and Repeat tracks are displayed in Btau_4.0. The GC percent track shows the percentage of G (guanine) and C (cytosine) bases in 5-base windows. The horizontal line at 41.7 in GC percent track represents the genome average of GC%. Probe locations are labeled like CHR25FS027220642 and etc.