Figure 3.

Relationship between age and physical distributions of complete elements. Insertions into the short arms of chromosomes II and IV were excluded for clarity. These arms contain extensive heterochromatin away from the centromeres, in nucleolar-organizing regions that juxtapose their telomeres, and in a knob [14]. In addition, their short length implies that the pericentromeric heterochromatin, which spans around 1-1.5 Mbp in each arm [68], corresponds to a substantially higher fraction of their total length than in the other eight arms.