Gone FISHin' for genes

Figure. Visualization of human genes using FISH. A DNA probe for single-copy gene is labelled with fluorescent dye and allowed to bind to normal metaphase chromosome spread (stained blue-white). Interphase nucleus also shows 2 copies of target gene. Inset: Amplification of genes in breast cancer cells. Green signals indicate normal number of copies of RB1 gene, and red signals indicate excessive number of copies of CCND1 (Cyclin D1) gene.