Fold-back model of inverted duplication formation.

<p>(A) 5′ and 3′ strands of the chromosome with telomeres (triangles) and centromere (circle) are shown. Short inverted sequences (grey rectangles with arrows) lie adjacent to the terminal deletion breakpoint. The inverted duplication mechanism occurs as described in the <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004139#s3" target="_blank">Discussion</a>. The resulting inverted duplication is indicated by orange arrows. (B) After a breakage-fusion-bridge cycle, the inverted duplication chromosome may be repaired as a terminal deletion, translocation, or ring chromosome.