A chromosome sorter is an instrument based on flow cytometry that can select and separate one chromosome from thousands of other chromosomes. A flow cytometer, usually called a fluorescence activated cell sorter (FACS), can identify different particles, cells and organelles by measuring the light they scatter, or the fluorescence they emit, as they flow through a laser beam in a fine stream.

In a typical chromosome sorting experiment, a concentrated suspension of metaphase chromosome stained with one or several DNA-binding fluorochromes is mixed with an excess of buffer called the sheath fluid. The mixture of labeled chromosomes is forced with a much larger volume of sheath fluid through a nozzle, creating a fine stream containing approximately one chromosome per buffer droplet. As each chromosome passes through a laser beam, it scatters the laser light and emits fluorescence from any dye molecule bound to it. Sensitive photo...