Figure 4.

Model for the role of homologous sequence elements in repair of double-strand breaks within the fragile region. Carcinogen-induced damage in the fragile region may cause double- or single-strand breaks at flexibility peaks, necessitating repair during replication. (A) The H1573 allele b is shown with black bars representing sequences retained in the cell, BP representing positions of deletion endpoints, and hatched regions representing the 79.4% homologous LINE1 elements near the breakpoints. (B) This simple model suggests how the homologous LINE1 elements might participate in a repair mechanism that would allow replication of the deleted H1573b allele.