Fragile X Syndrome

Introduction Fragile X syndrome is the most common progress to of inherited intellectual deliberation, seen in or so one in 1,cc males and one in 2,500 females. Males with breakable X syndrome usually subscribe to mental retardation and often exhibit characteristic physiologic features and behavior [Hagerman and Silverman, 1991; warren and Nelson, 1994]. Affected females exhibit a similar, precisely usually slight severe phenotype. The diagnosis of breakable X syndrome was originally found on the expression of a pteroylmonoglutamic acid-sensitive fragile site at Xq27.3 (FRAXA) induced in cell kitchen-gardening under conditions of folate deprivation. Cytogenetic analysis of metaphase spreads demonstrates the front extirpate of the fragile site in less than 60% of cells in most affected individuals. The cytogenetic test has constrainations, especially in testing for carrier status, and it exhibits a high degree of discrepancy between individuals and laboratories. Also, interpretation of the cytogenetic test for fragile X syndrome is complicated by the presence of other fragile sites in the same region of the X chromosome (FRAXD, FRAXE, and FRAXF). In 1991, the fragile X gene (FMR1) was characterized and found to contain a tandemly take oned trinucleotide successiveness (COG) near its 5 end. The mutation responsible for fragile X syndrome involves amplification of this repeat segment.

The number of CGG repeats in the FMR1 genes of the normal population varies from sise to approximately 50. There ar ii main categories of mutation, premutations of approximately 50 to 200 repeat s and full mutations of more than than appr! oximately 200 repeats. There is no clear boundary between the fastness limit of normal and the lower limit of the premutation range. For this reason, alleles with approximately 45-55 copies of the repeat are said to be in the grey zone. near alleles in this size range are unstable and dramatize from generation to generation, while others are stably inherited. If you want to hit a full essay, order it on our website: BestEssayCheap.com

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