Document Detail

Fragile X "gray zone" alleles: AGG patterns, expansion risks, and associated haplotypes.
MedLine Citation:
PMID:  8844060     Owner:  NLM     Status:  MEDLINE    
The risk for fragile X "gray-zone" alleles to expand appears to depend on the absence of stabilizing AGGs, which interrupt the CGG repeat region. To characterize such alleles better, we analyzed a series of 101 chromosomes with triplet repeat lengths ranging from 35 to 59 for variations in their AGG interspersion patterns. Among these, 11.9% had 3 AGGs, 59.3% had 2, 24.8% had 1, and 4.0% had 0. An inverse relationship between FMR1 repeat length and the number of interrupting AGGs was observed. Within the range of 35-44 repeats, 98.7% of alleles were found to have a pure CGG repeat length (PCGG) of less than 33. However, among alleles with 45-59 repeats, 50% were found to have 0 or 1 AGG and a PCGG of more than 33. Thus, gray-zone alleles with 45-59 repeats frequently have a long stretch of pure CGGs and thus are more likely to be unstably inherited than alleles with 35-44 repeats. We found length associations of PCGG with 2 flanking microsatellites, DXS548 and FRAXAC1: a PCGG < or = 20 was strongly associated with haplotype 20-19, whereas a PCGG > 20 was more strongly associated with the haplotype 25-21. This result could reflect a founder effect or a generalized instability of CGGs and microsatellites.
N Zhong; W Ju; J Pietrofesa; D Wang; C Dobkin; W T Brown
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of medical genetics     Volume:  64     ISSN:  0148-7299     ISO Abbreviation:  Am. J. Med. Genet.     Publication Date:  1996 Aug 
Date Detail:
Created Date:  1996-12-13     Completed Date:  1996-12-13     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7708900     Medline TA:  Am J Med Genet     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  261-5     Citation Subset:  IM    
Department of Human Genetics, New York State Institute for Basic Research, Staten Island 10314, USA.
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MeSH Terms
Fragile X Syndrome / epidemiology,  genetics*
Genetic Markers
Genetic Variation*
Risk Assessment
Risk Factors
Trinucleotide Repeats*
Grant Support
Reg. No./Substance:
0/Genetic Markers

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