Figure 4

Schematic representation showing the three mechanisms proposed for the formation and stabilization of the terminal inv dup 3q. A-B) Two possible mechanisms having in common a first step in gametogenesis with a double-strand break event at 3q, repaired by fusion of the two sister chromatids (U-loop) and giving rise to an acentric inv dup; A) Subsequent step would be the telomere capture from chromosome 12, a non-disjunction of the 12 homologous at meiosis I, leading to a gamete that after fertilization originated a trisomic zygote, that by cell rescue generated two cell lines; B) Other alternative mechanism would be the post-zygotic stabilization delay of the acentric inv dup; C) The third possibility is the generation of a terminal acentric inv dup as a result of a post-zygotic event at embryogenesis, which would necessarily lead to mosaicism.