Figure 2. The neocentromere of orang-utan chromosome 12.
Note the identical order of four sequentially arranged BAC-derived FISH probes indicated in yellow, blue, green and red (given in Supplementary Information section 8) between the normal (a) and neocentromere-bearing (b) configurations of orang-utan chromosome 12, despite discordant centromere positions. The left image of a and the right image of b are DAPI-only images that show the primary constriction of both chromosomal forms, indicated by the arrows. The neocentromere recruits centromeric proteins CENP-A and CENP-C and lies within a ∼225 kb gene-free and α satellite-free region. The neocentromere-bearing variant is polymorphic in both Bornean and Sumatran populations, suggesting the neocentromere arose before the Bornean/Sumatran split, yet has not been fixed in either species.