PRECONCEPTIONAL SEX SELECTION - PAST, PRESENT, AND FUTURE

Predetermination of sex in human and in farm animals is reviewed. Prec onceptional sex selection has generated great interest and controversy over the years. Medical and commercial benefits outweigh the ethical issues. Technology has not yet provided a routine method for separatin g the X- and Y-chromosome-bearing sperm. Flow cytometry is the only te chnique that produces a clinically significant enrichment of X- or Y-b earing spermatozoa. However, concern has been raised about the methodo logical implications of the flow technique because of the use of DNA s tains and UV light. Some other techniques, such as gradient columns, a ppear to produce a slight enrichment of one type of sperm over the oth er, but this level of enrichment appears unlikely to affect the sex ra tio at birth. It thus remains speculative whether 100% pure preparatio n of X or Y sperm can be obtained unless a major improvement in method ology is achieved. Fluorescence in situ hybridization (FISH) and polym erase chain reaction (PCR) are currently the methods of choice for eva luating the validity of the sex selection procedure. In view of the ex traordinary pace of the technological and scientific progress, it can be expected that the clinical and commercial application of the techno logy of preconceptional sex selection by X and Y sperm separation will be a reality in near future.