Word: sperm
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...Virginia scientists, though, adapted a technique that has been used for more than a decade to select the sex of cows, horses and pigs. Working with U.S. Department of Agriculture scientist Lawrence Johnson, who invented the method, they stained sperm with a fluorescent dye that latches onto DNA. Measuring the glow of the sperm cells under laser light, they could gauge how much genetic material each one carried. As it happens, X chromosomes have about 2.8% more DNA than Ys. Once the sperm had been distinguished this way, an automated sorting machine separated the Xs from the Ys, and doctors...
...take so long to try the method in humans? The delay was not because of ethical concerns, though some have been raised (see Viewpoint), but because the DNA difference in animal sperm is larger, and thus much easier to measure...
...particular sex, either to bring "gender balance" to their family or to help them avoid sex-linked genetic diseases for which their offspring could be at risk. The procedure took no more than a day and cost a non-reimbursable $2,500 a try. "I actually watched the sperm enter my body on the screen of the ultrasound machine," marvels Monique Collins, 33, of Gainesville, Va., one of the program's first successes...
Although the technique yielded a relatively meager harvest of up to 300,000 sperm for each attempt (in contrast to 100 million or more in a natural ejaculation), the results were impressive. Of 14 pregnancies involving couples who wanted girls, the researchers report, 13 produced females. Says Fugger: "We're talking about increasing your chances of getting girls five- or sixfold." No formal report has yet been published on selecting a male baby, which, to the surprise of the scientists, was not the choice of most participants. But preliminary results suggest male selection will work 65% of the time...
...Scientists have developed a way to separate sperm that carry the Y chromosome, which produces males, from sperm that carry the X chromosome, which produces females. So couples can now choose a child's sex. How are the Y sperm different...