Spontaneous nonreciprocal translocations arising in NHEJ-deficient cells. (a) Lig4−/− MEF. An unusual chromatid interaction is seen by DAPI staining (Left), which is comprised of at least two chromosomes visible after hybridization with the SKY probe mixture (Center). Spectral analysis yields classified colors (Right), indicating that this is a complex translocation involving material from three different chromosomes. From left to right, the chromosomal material is 15, 8, and X. (b) The cell of origin was from a dispersed abdominal organ block of a midgestation Lig4−/− embryo. The cell was not cultured or exposed to colcemid. The exact cell type is not known. DAPI staining (Left), visible colors after SKY probe hybridization (Center), and spectral analysis (Right) are shown. The chromosome arose from a simple t(5:6) translocation. (c) Lig4−/−p53−/− MEF. Complex translocation involving material from as many as four different chromosomes. DAPI staining (Left), visible colors after SKY hybridization (Center), and classified colors after spectral analysis (Right) are shown. The chromosomal material, from top to bottom, is 13, 7, 17, and 11.