It’s a beautifully simple idea. Since sperm bearing a Y chromosome (the onethat creates little boys) contains nearly 3 percent less DNA than itsfemale X chromosome counterpart, why not sort sperm by its genetic weight– and stack the deck for couples who want to choose the sex of theirchild? Easier said than done, of course. But that’s precisely the techniquethat a Fairfax, Va., fertility center is set to reveal Wednesday in thejournal Human Reproduction. Based on the information released so far, thisappears to be the most reliable gender-selection process ever developed.
The technique perfected by the not-for-profit Genetics & IVFInstitute involves staining sperm cells with a DNA-sensitive fluorescentdye and then passing them single file through a laser beam. The cells aresorted based on the amount of light reflected by the fluorescent DNA. It’spainstaking work — sorting a single batch takes the better part of a day– but the results speak for themselves: Of 14 pregnancies produced so farfor couples who wanted a girl, 13 fetuses were female. Not entirelyfoolproof, but pretty close.