Fig. 4

Schematic representation of mechanisms leading to inv-dup del translocation (2p;5p) and inv-dup del(5) in case 4. The red line indicates the breakage event, the deletion on chromosome 5 is in blue, the portion of donor chromosome 2 is in yellow, the telomeric sequences are in grey, the neo-telomere is in red. A breakage event on chromosome 5p A leads to the deleted chromosome B that stabilizes its sticky end by forming an unstable intermediate dicentric C whose asymmetric breakage results into an inv-dup del and a deleted chromosome D; the inv-dup del stabilizes by capturing a large portion of chromosome 2p containing the telomeric sequence, leading to the inv-dup del translocation (2p;5p) E, G. Two mechanism may be considered to explain also the presence of the smaller inv-dup del (5): the mechanism 1 (upper) presupposes the loss of the translocated chromosome 2 portion with stabilization of the inv-dup del (5) by de novo telomere synthesis F, the mechanism 2 assumes two independent repair events in the two daughter cells of the mitotic division, which stabilize the inv-dup del either by translocation with 2p in one cell daughter (G left) or by neo-telomere formation in the other ones (H left)