Y-Sperm Fluorescence Lab Report

The basic principles are simple; the X-sperm contains more DNA than the Y-sperm. Although this difference is small, it is possible to measure DNA content of individual sperm with sufficient accuracy to distinguish between X- and Y-sperm with about 90% accuracy for 50% of the sperm. Therefore, about half of the sperm are discarded as unsexable. The DNA content of sperm is determined using a fluorescing dye, Hoechst 33342 that readily penetrates the sperm cell membrane and binds to the DNA stoichiometrically. Thus, X-sperm ends up with about 4% more dye bound to their DNA than Y-sperm. This dye only fluoresces when exposed to a particular wavelength of light, and this is usually provided by an expensive laser. The fluorescence is measured by a detector and analyzed by computer. Since X-sperm have 4% more DNA, and therefore, bind more dye than Y sperm, they give off 4% more fluorescence, which the computer can recognize.
The principles just discussed are combined to make a system to sex sperm. The basic instrument used is a flow cytometer/cell …show more content…
It consists of a pump to move the fluid containing sperm past a detector of fluorescence. A laser provides the correct wavelength of light to cause fluorescence without damaging the DNA. A powerful computer also is needed to analyze the fluorescence. The cell sorting part of the system works as follows: when the stream of fluid exits the flow cytometer, it is broken into little droplets by a vibrator, forming about 70,000 to 80,000 droplets per second. About one-third of the droplets contain a sperm and about two-thirds are empty; a few droplets contain two or more sperm. If a droplet contains an X-sperm as analyzed by the computer, a positive electrical charge is added to the droplet; if the droplet contains a Y-sperm, a negative charge is added; and if the droplet contains no sperm, multiple sperm, damaged sperm, or