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− | == Principle ==
| + | <big><center>[[Reproductive System|'''BACK TO REPRODUCTIVE SYSTEM''']]</center></big> |
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− | * X and Y chromosomes contain different quantities of DNA.
| + | <big><center>[[Reproductive_System#Reproductive_Technologies|'''BACK TO REPRODUCTIVE TECHNOLOGIES''']]</center></big> |
− | * X-bearing sperm contain 2.8-4.2% more DNA (species dependent) than Y-bearing sperm.
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− | * This allows them to be sorted into two subpopulations.
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− | * Separation requires the uptake of DNA stain/dye called Fluorochrome into living and dead sperm.
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− | * X-bearing sperm take up more dye than Y-bearing sperm.
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− | * Vital dyes emit light at a specific wavelength when excited or activated.
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− | ** X-bearing sperm will emit a larger signal than Y-bearing sperm.
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− | * This allows the sperm to be sorted by '''flow cytometry'''.
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− | == Flow Cytometry ==
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− | [[Image:Semen Sorting.jpg|thumb|right|150px|<p>Schematic Diagram to show Semen Sexing by Flow Cytometry</p><sup> ©Nottingham University 2008</sup>]]
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− | * Ejaculated spermatozoa are treated with a DNA dye (fluorochrome).
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− | * X-bearing sperm absorb more dye than Y-bearing sperm.
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− | * X-bearing sperm thus emit more intense light when excited by a laser.
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− | * Sperm are also treated with a dye that greatly suppresses the signal from dead sperm.
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− | ** Dead sperm are therefore identified and rejected.
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− | * Once spermatozoa enter the flow cytometer chamber, they pass single-file through a small nozzle.
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− | * At a region just outside the nozzle, an excitation laser beam activates the fluorescent dye in each sperm.
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− | * Each live sperm produces an emission with an intensity that is directly related to the quantity of DNA within the sperm head.
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− | ** X-bearing live sperm produce more intensity.
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− | * 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.
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− | * 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).
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− | * 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.
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− | * Dead sperm are discarded into the centre tube.
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− | * At the end there are three vessels that contain sperm:
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− | ** One contains a high proportion of X-bearing sperm.
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− | ** One contains a high proportion of Y-bearing sperm.
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− | ** One contains dead sperm
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− | [[Category:Reproductive Technologies]]
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− | [[Category:Bullet Points]]
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