Chromosome rearrangements. Coloured scanning electron micrograph (SEM) of chromosomes after treatment with etoposide. Chromosomes normally consist of two identical chromatids joined at a centromere. These chromosomes have suffered numerous breaks, resulting in the deletion and interchanging of fragments of the chromosomes. Etoposide is a drug that is used to treat some types of cancer, mainly testicular and small-cell lung cancer. It prevents malignant (cancerous) cells from spreading by interfering with cell division mechanisms, eventually causing cell death. It also physically damages chromosomes, by causing breaks. These aberrations can also be lethal. Magnification: x7,800 at 10cm wide.