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Semen Sexing - Anatomy & Physiology (view source)
Revision as of 13:48, 5 July 2012
, 13:48, 5 July 2012→Flow Cytometry
== Principle ==
* X and Y chromosomes contain different quantities of DNA.
* X-bearing sperm contain 2.8-4.2% more DNA (species dependent) than Y-bearing sperm.
* This allows them to be sorted into two subpopulations.
* Separation requires the uptake of DNA stain/dye called Fluorochrome into living and dead sperm.
* X-bearing sperm take up more dye than Y-bearing sperm.
* Vital dyes emit light at a specific wavelength when excited or activated.
** X-bearing sperm will emit a larger signal than Y-bearing sperm.
* This allows the sperm to be sorted by '''flow cytometry'''.
== Flow Cytometry ==
[[Image:Semen Sorting.jpg|thumb|right|150px|<p>Schematic Diagram to show Semen Sexing by Flow Cytometry</p><sup> ©Nottingham University 2008</sup>]]
* Ejaculated spermatozoa are treated with a DNA dye (fluorochrome).
* X-bearing sperm absorb more dye than Y-bearing sperm.
* X-bearing sperm thus emit more intense light when excited by a laser.
* Sperm are also treated with a dye that greatly suppresses the signal from dead sperm.
** Dead sperm are therefore identified and rejected.
* 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.
** One contains dead sperm
[[Category:Reproductive Technologies]]
[[Category:Bullet Points]]