In genetics, certain terms sometimes mask what scientists do not yet understand, such as "junk DNA." Similarly, the chromosomal regions just proximal to the tips--the subtelomeres--have been dubbed "buffers," ill-defined DNA sequences that somehow support the telomeres, which control the cell cycle and cellular aging. A team of researchers from the Wistar Institute in Philadelphia, the University of California, Irvine, and John Radcliffe Hospital in Oxford, UK, has used single-copy sequences in the subtelomeric regions to anchor them to and extend the draft genome sequence to the telomeres.1 And in what is becoming a repeated theme in genomics, they were surprised at what they found.

Highly repetitive genome regions are notoriously difficult to assign to a particular chromosome, let alone sequence, because assembly programs can overlap them in many ways and places. So it is for the telomeres, the tips of chromosomes that in humans and other vertebrates consist...

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