FISH analysis of the t(8; 13) chromosome translocation from R.B. Somatic cell hybrids RBF1 (A) and RBF24 (B) were stained with DAPI (blue) in each case. Partial metaphase spreads are shown in each case after chromosome painting. The green signal represents chromosome 8 material, and the red signal is from chromosome 13. In RBF1 (A), the der(8) can be clearly seen (top), as can the normal copies of chromosomes 8 (green) and 13 (red). In hybrid RBF1 (B), only the normal 8 is seen, as well as the der(13). When YAC 959A4 from chromosome 8 is hybridized to cells from RBF1 (C) and then cells are identified that contain both of the derivative chromosomes, the hybridization signal from the YAC is seen (red) on the normal copy of chromosome 8 (bottom right), as well as the 2 derivative chromosomes (top left). In these cells, chromosome 8 material is painted green. The DAPI image from the partial metaphase chromosome spread shown in C has been processed in D to reveal the typical G-band appearance of the chromosomes. The derivative chromosomes therefore can be clearly identified. The red and green signals have been superimposed on this black and white image.