Organization of HSAT I/Alu/AT-rich sequence in the LCR22s. The LCR22s are made of blocks or modules shown here in the block structures (LCR22-2 is 241,823 bp; LCR22-3 size is not determined; LCR22-4 is 245,258 bp; Babcock et al. 2003). The different colors represent the different gene portions the LCR contains and its organization: USP18, pink; BCR, blue; GGT2 (found in LCR22-2 and LCR22-4, while GGT1 is found in LCR22-8) and GGTLA1, yellow; IGSF3 (pseudogene; real gene found on chromosome 1p13.1), orange. The blocks found under the LCR blocks represent the known HSAT I elements. These HSAT I elements are found in both orientations and are associated with Alus and AT-rich sequence. The orientation is centromere to telomere of 22q11.2 from left to right. The numbers represent the percent identity between the HSAT I’s, using the most centromeric element as reference.