Using FISH to detect chromosomal abnormalities in interphase nuclei.

(a) The duplication of a small portion of chromosome 17 that causes Charcot-Marie-Tooth syndrome is evident from the appearance of three, rather than two, red signals in this nucleus. The green spots mark a sequence outside the duplication. (b) The translocation that creates a fusion of the BCR (on chromosome 22) and ABL (on chromosome 9) genes in the Philadelphia chromosome is evident from the close juxtaposition of one pair of green and red signals. These signals were generated using FISH probes for sequences located near these two genes, respectively. der(22) is the Philadelphia chromosome. Only the relevant portions of the normal and abnormal chromosomes are shown in the diagram below each panel.