Wednesday 4 July 2012

144.TRINUCLEOTIDE REPEAT IN FRAGILE X SYNDROME

A.CAG
B.CGA
C.CGG
D.CTG

ANS:CGG


The first triplet disease to be identified was fragile X syndrome, which has since been mapped to the long arm of the X chromosome. At this point, there are from 230 to 4000 CGG repeats in the gene that causes fragile X syndrome in these patients, as compared with 60 to 230 repeats in carriers and 5 to 54 repeats in unaffected individuals. The chromosomal instability resulting from this trinucleotide expansion presents clinically as mental retardation, distinctive facial features, and macroorchidism in males.

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