CHROMOSOME PAINTING USING FISH (FLUORESCENCE IN-SITU HYBRIDIZATION) WITH CHROMOSOME-6-SPECIFIC LIBRARY DEMONSTRATES THE ORIGIN OF A DE-NOVO6Q+ MARKER CHROMOSOME

We report the application of chromosome painting using FISH (fluoresce nce in situ hybridization) to demonstrate the origin of a de novo 6qmarker chromosome. A girl with a mental retardation/multiple malformat ion syndrome was shown to have the karyotype 46,XX, 6q+. Banding analy sis could not determine the origin of the extra chromosomal material. Using FISH with a chromosome-6-specific library we showed that the mar ker chromosome was completely painted, indicating an origin from chrom osome 6. The child's phenotype was compared with previously reported c ases with partial chromosome 6 trisomy. A clinically recognized syndro me emerged, although she apparently also demonstrated novel features.