Figure 5

Illustration of the unzipping and zipping on gene trees and adjacency graphs. A) Prior to linearization (left of the black arrow), the gene g exists in one copy in the ancestor (vertical gray line on the tree) and two independent duplications occurs in its descendants (green hollow squares). In the ancestral adjacency graph above each of g extremities displays two neighbors. Unzipping (right of the black arrow) modifies the tree so that there are two ancestral copies g and g′ each corresponding to a different path in the ancestral adjacency graph (losses in the tree are displayed as red crosses). B) Prior to linearization (left of the black arrow), two ancestral copies of the same gene h and h′ exist in the ancestor (vertical gray line on the tree; losses in the tree are displayed as red crosses). In the ancestral adjacency graph above the extremities of h and h′ each share a neighbor, forming a non-linear pattern. Zipping (right of the black arrow) modifies the tree so that there only one ancestral copy h _d followed by independent duplications in its descendants (green hollowed squares), forming one linear path in the ancestral adjacency graph.