Figure 1.

Cytogenetic map of chromosome 2 heterochromatin, showing the extent of the I-R-induced deficiencies along the heterochromatin of the right arm. Thirteen cytologically distinct regions, designated h35 to h46, can be resolved in chromosome 2 heterochromatin (24). Filled areas represent the Hoechst 33258-bright regions; the shaded boxes represent regions of intermediate fluorescence, and the open boxes are regions of dull fluorescence. Only the heterochromatic regions are shown. Above the diagram are bars indicating the mapping of 13 vital heterochromatic genes. The genes in the left arm of chromosome 2 (2Lh) are indicated from top to bottom according to their left to right mapping along the chromosome. The extent of the I-R-induced deficiencies was determined cytogenetically as described in detail elsewhere (24, 30) and is represented by thick lines (below). 2L, left arm; 2R, right arm; C, centromeric region.