Schematic structure of the SPANX-A/D locus. The scheme shows the positions of SPANX (red) and LDOC1 (green) genes. Boxes mark the positions of segmental duplications, and the box orientation corresponds to the direction of transcription of the embedded SPANX gene. The segment is drawn to scale and corresponds to a 750 kb-long genomic segment (chrX:138750001–139500000). Fragments isolated by TAR cloning are shown as well. The positions relative to the centromere (cen) and telomere (qter) are marked.