Chimpanzee chromosomes: retrotransposable compound repeat DNA organization (RCRO) and its influence on meiotic prophase and crossing-over

The terminal C-bands that are a specific feature of chimpanzee chromosomes were dissected using a molecular cytogenetic technique, PRINS, with primers for telomeric sequences, subterminal satellite, and retrotransposable elements (HERV-K and -W). These DNA elements jointly formed a large block of retrotransposable compound repeat DNA organization (RCRO) at the terminal C-band regions of 30 chromosomes, and are also located at the centromeric regions of some chromosomes. Additionally, a block consisting of all members of the RCRO has transposed to the middle (q31.1) of the long arm of chromosome 6, and three members, the subterminal satellite and the two HERVs, have integrated into the proximal region (q14.4) of the long arm of chromosome 14. Terminal RCROs seem to induce and prolong the bouquet stage in meiotic prophase, and to affect chiasma formation, together with interstitial RCROs. It is also postulated that RCROs may cause a position effect to gene expression, resulting in gene silencing and/or late replication.