Fragile X Syndrome and Fragile Sites
Fragile X syndrome is a relatively common, yet—until recently—poorly understood inherited condition characterized by variable degrees of learning and social disability. First discovered in 1943 (when it was known as the Martin-Bell syndrome), it derives its name from its frequent association with a rare folate-sensitive fragile site (FRAXA) localized near the distal tip of the long arm of the X chromosome (Fig. 1) at Xq27.3, later also confirmed as the site of the gene locus. In fact, there are two distinct conditions associated with expressed site fragility in this chromosomal segment: the FRAXE site is difficult to distinguish from FRAXA by conventional cytogenetics, but high-resolution methods map it slightly distal at Xq28. Some, but not all, properties of the FRAXA locus also apply to FRAXE; the primary discussion in this article will be of FRAXA, but the distinctive characteristics of the FRAXE locus will be pointed out wherever relevant.
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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.