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American Journal of Human Genetics logoLink to American Journal of Human Genetics
. 1995 Dec;57(6):1408–1413.

Expansion of the CGG repeat in fragile X in the FMR1 gene depends on the sex of the offspring.

D Z Loesch 1, R Huggins 1, V Petrovic 1, H Slater 1
PMCID: PMC1801407  PMID: 8533771

Abstract

Analysis of 139 mother-to-offspring transmissions of fragile X CGG triplet repeats revealed that the repeat expansion is enhanced in mother-to-son transmissions compared with mother-to-daughter transmissions. Evidence has been based on analysis of mother-offspring differences in the size of repeat (in kb), as well as on comparisons between proportions of male and female offspring with premutations, and full mutations, inherited from mothers carrying a premutation. Mean difference in the repeat size from mother-son transmissions was 1.45 kb, compared with mother-daughter transmissions of 0.76 kb. The difference is due primarily to a greater proportion of male than female offspring with full mutation from the premutation mothers and also to a higher frequency of reduction in repeat size from mothers to daughters than from mothers to sons. Our findings suggest the possibility of an interaction of the normal X homologue in a female zygote with the FMR1 sequence on the fragile X during replication to account for the lower level of expansion in mother-to-daughter transmissions relative to mother-to-son transmissions.

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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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