FIG. 2.
Experimental system to study DSB repair involving tandem arrays. An HO cut site is introduced into a KpnI site of the chromosomal endogenous LEU2 gene. The HO gene can be expressed from an inducible promoter and will cut the LEU2 gene (A). The structures of the templates are shown as follows: no homologous template (B); plasmid LEU2 template (C); plasmid LEU2 templates containing eight D. melanogaster 5S genes in a tandem array (D), two 5S arrays surrounding the D. melanogaster white gene (E), the 5′ part of the white gene (F), or the entire white gene (G); chromosomal LEU2 template (H); and chromosomal leu2 template with a 9.1-kb insert corresponding to two 5S arrays surrounding the white gene (I). Shaded box, LEU2 gene; open box, one D. melanogaster 5S gene (375 bp); solid box, D. melanogaster white gene; open circle, centromere. The number of repeats in each 5S array is given above the array.