Speed Trap

As SFARI reported this week, new DNA tests may bring us closer to universal screening for fragile X syndrome in pregnant women and newborns. But the tests also raise an ethical conundrum: they pick up abnormalities in some babies who won't develop symptoms until adulthood, if at all.People with fragile X syndrome carry more than 200 repeats of a particular genetic sequence in the FMR1 gene, located on the X chromosome. The new DNA-based methods detect the disorder by counting the number of repeats.But there’s a hitch. The tests also detect 'premutation' carriers, who have only 55 to 200 repeats and often don't show symptoms in childhood. Also, some girls who carry more than 200 repeats never show any symptoms because their second, healthy X chromosome compensates.Read more at...SFARI, October 2010.