The predetermination of embryonic sex using flow cytometrically separated X and Y spermatozoa

A review is given of the predetermination of sex in variousdomestic animals and in the human using sperm samples enrichedfor X- and Y-chromosome bearing spermatozoa obtained by flowcytometry and cell sorting. A comparison of other putative methodsof sperm separation is made. In separating human X and Y spermatozoa,measurements of the DNA content in each individual gamete usingthe Hoechst fluorochrome 33342 remains the only validated method.The difference in DNA content between human X and Y spermatozoais 2.8%, and cell sorters have been adapted to take accountof this and the asymmetrical nature of the sperm head. DNA analysesand PCR have been used to validate the method for animal spermatozoa.In the human, fluorescence in-situ hybridization (FISH) hasconfirmed sorting accuracy. Many correctly-diagnosed normaloffspring have been born in various animal species and any potentialmutagenic or cytotoxic effects are being closely monitored asare the cost and efficiency of the technology.