Evolution of repeat unit arrays in human, chimpanzee and orangutan SVA subfamilies. (A) The consensus repeat unit (RU) arrays for each of the subfamilies are superimposed on a network based on alignment of the consensus sequences of the subfamilies’ SINE-R domains (, details as well as a complete network for orangutan SVAs are provided in Additional file 1: Figure S3). Network branches are not drawn to scale with respect to the evolutionary distance. For reasons of clarity only the evolutionary youngest orangutan subfamilies are shown. (B) Repeat unit schemata for the ten SVA_E elements analyzed. Conserved arrays at the 5’ and 3’ ends are highlighted in grey; internal arrays are boxed. K’ denotes a K-type RU with a slightly divergent sequence that is always found at the 5’ end of the arrays.