Figure 2.

The mechanism of gene amplification involving B/F/B cycles. B/F/B cycles are initiated when sister chromatids fuse following the loss of a telomere. The resulting dicentric chromosome forms a bridge during anaphase and breaks again, continuing the cycle until the chromosome obtains a new telomere. Breakage at locations other than the site of fusion results in amplification of sequences in one daughter cell and deletions in the other daughter cell. The distance between the amplified arrays is dependent upon the distance of the break from the site of fusion. The telomeres (gray squares), centromeres (circles), and orientation of the subtelomeric sequences (arrow) are shown.