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. 1993 Feb;52(2):297–304.

Linkage disequilibrium between the fragile X mutation and two closely linked CA repeats suggests that fragile X chromosomes are derived from a small number of founder chromosomes

C Oudet, E Mornet, J L Serre, F Thomas, S Lentes-Zengerling, C Kretz, C Deluchat, I Tejada, J Boué, A Boué, J L Mandel
PMCID: PMC1682195  PMID: 8094266

Abstract

In order to investigate the origin of mutations responsible for the fragile X syndrome, two polymorphic CA repeats, one at 10 kb (FRAXAC2) and the other at 150 kb (DXS548) from the mutation target, were analyzed in normal and fragile X chromosomes. Contrary to observations made in myotonic dystrophy, fragile X mutations were not strongly associated with a single allele at the marker loci. However, significant differences in allelic and haplotypic distributions were observed between normal and fragile X chromosomes, indicating that a limited number of primary events may have been at the origin of most present-day fragile X chromosomes in Caucasian populations. We propose a putative scheme with six founder chromosomes from which most of the observed fragile X–linked haplotypes can be derived directly or by a single event at one of the marker loci, either a change of one repeat unit or a recombination between DXS548 and the mutation target. Such founder chromosomes may have carried a number of CGG repeats in an upper-normal range, from which recurrent multistep expansion mutations have arisen.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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