** Dead sperm are therefore identified and rejected.
** Dead sperm are therefore identified and rejected.
−
* Once spermatozoa enter the flow cytometer chamber
+
* Once spermatozoa enter the flow cytometer chamber, they pass single-file through a small nozzle.
+
* At a region just outside the nozzle, an excitation laser beam activates the fluorescent dye in each sperm.
+
* Each live sperm produces an emission with an intensity that is directly related to the quantity of DNA within the sperm head.
+
** X-bearing live sperm produce more intensity.
+
* A light sensing device is coupled to a computer that determines the intensity of light emission by each sperm and the order of passage of each sperm through a column below the nozzle.
+
* When the sperm pass through charged plates, they are assigned either a positive or negative charge depending on their DNA content (X or Y chromosome).
+
* When the microdroplet containing a single sperm passes through an electromagnetic field the computer applies an appropriate charge and directs the droplet (and sperm) to one side or the other.
+
* Dead sperm are discarded into the centre tube.
+
* At the end there are three vessels that contain sperm:
+
** One contains a high proportion of X-bearing sperm.
+
** One contains a high proportion of Y-bearing sperm.