Word: x
(lookup in dictionary)
(lookup stats)
Dates: all
Sort By: most recent first
(reverse)
...addition, new research has revealed that relatives who carry the fragile X trait, like Max's mother and grandfather, may themselves be affected by it. At the National Institutes of Health (NIH), a new panel has been charged by Congress to direct research into FXS and related conditions. "We hope to learn lessons that may be applicable to helping people with Huntington's disease, Alzheimer's and myotonic dystrophies too," says Tiina Urv, who heads the panel. Research on the FXS family of disorders may also yield clues to some forms of infertility...
Most of us move through our days with only a vague awareness of our genetic endowment, fretting perhaps over a familial tendency toward heart disease or beaky noses. But families affected by fragile X can discuss their genome with startling specificity. Their key concern is a small strip of DNA on the long arm of the X chromosome. Normally, humans have five to 55 repetitions of the nucleotides CGG (cytosine, guanine, guanine) in this region. But for unknown reasons, the number of CGG repeats can expand beyond normal as the DNA is copied from mother to child...
Cari, for instance, has one normal X chromosome (with 24 repeats), inherited from her mother, and another with an abnormal 85 repeats, inherited from her father, who has 89 repeats. Cari's son Max has 363. Any number greater than 200 causes full-blown fragile X syndrome (so named because, under a microscope, the expanded X chromosome may look bent to the point of breaking). The reason boys are more likely than girls to develop major symptoms is that girls carry a pair of X chromosomes, which means that if one is defective, the other can compensate. Boys, however, carry...
People like Cari and her father, with 55 to 200 repeats, are considered carriers of a fragile X "premutation." Carriers are relatively common: about 1 in 250 women and 1 in 800 men have the premutation, though some studies suggest the prevalence is higher. Until recently no one worried too much about those numbers, since carriers were thought to be unaffected...
...pediatrician Hagerman who first noticed in the late 1990s that mothers of kids with FXS often reported that their father was experiencing neurological symptoms. "I thought, This can't be a coincidence," she recalls. At an FXS conference in 2000, Hagerman asked some 100 fragile X family members if an older male relative was having problems with balance, tremors or dementia. About a third of the audience members shot their hands into the air. Within a few years, a newly recognized genetic disorder called FXTAS (fragile X--associated tremor, ataxia syndrome) was part of the literature, though the illness...