University of wisconsin-madison

Sperm Sexing

Sperm sexing depends on the difference in the amount of DNA  in X and Y sperm. X sperm have 2.8-7.5% more DNA than Y sperm depending on the species. The X chromosome is bigger than the Y chromosome. Fluorescent dyes which bind to the DNA are used to differentiate the amount of DNA a cell has.

The sperm sorting technique was developed by L. Johnson (ARS-USDA, Beltsville, MD) in 1989. Dr. Johnson was originally from Luck Wisconsin. The first filly (Call Me Madam) born from sexed semen was in 1998 (XY,Inc and CSU, CO). The sexed semen was surgically placed in the oviduct. The four foals born the next year from sexed semen resulted from deep uterine insemination of 25 million sperm. Research continues to increase the yield and viability of sexed semen. It will likely be available commercially but expect it to be expensive.

Sperm Sexing Procedure

  1. Sperm are dyed with DNA dye. X bearing cells bind more dye than Y bearing cells.
  2. Only one sperm is released in a drop.
  3. A laser beam excites the dye and the sperm gives off light proportional to its DNA content
  4. The drop is charged depending on the light intensity.(X sperm give off more light than Y sperm)
  5. The drops pass through a pair of electrodes and the charged drops sorted into different tubes.
  6. Inseminate Mare- deep uterine deposit
diagram of cell sorter- flow cytometer with ability to charge cells with different dna content

next back