Fragile X Syndrome Flashcards
____ is the commonest inherited form of significant learning disability, w/ a prevalence of approximately ____ males.
Fragile X syndrome; 1 in 5000 males
Fragile X syndrome is caused by an unstable length mutation in the ____ repeat in the 5 ′ UTR of the ____ gene.
CGG trinucleotide repeat (normally 6 – 54 repeats, median 30 repeats); FMR1 gene.
In the full mutation associated Fragile X syndrome, FMR1 becomes hypermethylated due to ____, transcription is suppressed and no FMR protein (FMRP) is generated.
cytosine methylation
T/F. Paradoxically, however, w/ premutations (consisting of 55 –200 repeats), the long - term clinical effects may result from a toxic effect of the FMR1 transcript rather than its absence.
True.
The normal physiological role of FMRP is believed to be the regulation, by ____, of ____.
mRNA binding; local neuronal protein translation
Under ___ or ___ starvation, cytogenetic analysis in males or females who have learning disability & the full fragile X mutation usually reveal a ‘fragile site’ at the ____ in 10-40% of cells.
thymidine; deoxycytidine starvation; Xq27.3
Male & female carriers of the premutation (small length mutations) usually have an IQ within the normal range. Potential long - term effects have been reported, however, including, in males, _____ &, in females, a ____.
progressive fragile X tremor/ataxia syndrome (FXTAS); premature menopause
T/F. The daughters of those clinically normal males who possess the premutation (‘ normal transmitting males ’) will inherit the premutation, which may then be passed on either intact or with expansion to the full mutation.
True.
T/F. For mothers w/ the full mutation, one - half of their sons will be affected and one – half of their daughters will receive the full mutation (w/ about one - half of these daughters having learning disabilities to some extent).
True.
T/F. For mothers w/ the premutation, the risk of expansion to the full mutation at meiosis depends upon the size of the mother ’ s premutation.
True.
