Document Detail

Recurrent and unexpected segregation of the FMR1 CGG repeat in a family with fragile X syndrome.
MedLine Citation:
PMID:  8834253     Owner:  NLM     Status:  MEDLINE    
Fragile X syndrome, the most common cause of hereditary mental retardation, results from amplification of a CGG trinucleotide repeat in the FMR1 gene. The transmission of the CGG repeat from premutated individuals to their premutated descendants is usually unstable, showing an increase in the size of the repeat. We report here a family which exhibits recurrent and unexpected transmission of the maternal premutation to three daughters. The first daughter exhibited mosaicism with two premutated alleles, one contracted and the other expanded. The second daughter showed a reversion from the maternal premutation to the normal range, and the third carried an expanded premutated allele associated with an expanded paternal allele within the normal range. These variations in the size of the CGG repeat may result from many different mechanisms such as DNA polymerase slippage on the leading or lagging strand during replication, large contractions of repeats on the parental strand during replication, or recombination through unequal crossover between sister chromatids. Our results suggest that the variation of the CGG premutated alleles in this family may be the result of intrinsic instability associated with a trans-acting factor such as a mismatch repair gene product.
E Mornet; C Chateau; A Taillandier; B Simon-Bouy; J L Serre
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Human genetics     Volume:  97     ISSN:  0340-6717     ISO Abbreviation:  Hum. Genet.     Publication Date:  1996 Apr 
Date Detail:
Created Date:  1996-12-03     Completed Date:  1996-12-03     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7613873     Medline TA:  Hum Genet     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  512-5     Citation Subset:  IM    
Centre d'Etudes de Biologie Prénatale SESEP, Université de Versailles, France.
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MeSH Terms
Fragile X Mental Retardation Protein
Fragile X Syndrome / genetics*
Nerve Tissue Proteins / genetics*
Polymerase Chain Reaction
RNA-Binding Proteins*
Repetitive Sequences, Nucleic Acid*
Reg. No./Substance:
0/FMR1 protein, human; 0/Nerve Tissue Proteins; 0/RNA-Binding Proteins; 139135-51-6/Fragile X Mental Retardation Protein

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