YAC clone contigs covering 5 Mb of a repeat sequence island on the mouse X chromosome.

We have initiated work towards the construction of YAC clone contigs across a repeat sequence island region on the mouse X Chromosome (Chr). The repeat sequence island region-the 141 island-located at band A3 contains 50 copies of a localized long complex repeat unit (LCRU). We have isolated 87 YAC clones from the 141 island and have used a dual faceted approach towards the construction of contigs across the repeat sequence island. First, we have identified YAC clones originating from the same region of the island by the identification of commonly held LCRU restriction site variants. Second, we have constructed rare cutter restriction maps of each YAC clone. Taken together, we have been able to assemble one large contig of 2.8 Mb and a number of smaller contigs. In total, contigs covering 5Mb of the island region have been identified. The island region would appear to represent a major component of the A3 Giemsa dark band on the mouse X Chr.