Related Experiment Video
Updated: Jul 31, 2026
11:29
Modified Terminal Restriction Fragment Analysis for Quantifying Telomere Length Using In-gel Hybridization
Published on: July 10, 2017
Improved fluorescent PCR-based assay for sizing CGG repeats at the FRAXA locus
C Houdayer1, A Lemonnier, M Gerard
1Laboratoire de Biochimie et Biologie Moléculaire, Hôpital Necker Enfants-Malades, Paris, France. biochimie.trousseau@trs.ap-hop-paris.fr
Clinical Chemistry and Laboratory Medicine
|June 16, 1999
Summary
A new fluorescent PCR assay accurately sizes CGG repeats in the FMR1 gene, offering a faster alternative to Southern blot for diagnosing Fragile X syndrome in individuals with intellectual disability.
Area of Science:
- Genetics
- Molecular Biology
- Neuroscience
Background:
- Fragile X syndrome is the most common inherited cause of intellectual disability.
- It results from an expanded CGG repeat in the FMR1 gene.
- Current diagnostic methods like Southern blot are time-consuming.
Purpose of the Study:
- To develop a rapid and precise fluorescent PCR-based assay for sizing CGG repeats.
- To provide an alternative to Southern blot for Fragile X syndrome diagnosis.
Main Methods:
- Utilized a fluorescently labeled reverse primer and Expand Long Template PCR.
- Incorporated dimethyl sulfoxide (DMSO) and 7-deaza-dGTP for optimal amplification.
- Tested the assay on males and females across a range of repeat sizes.
Main Results:
- The assay precisely determined CGG repeat numbers from normal to premutation sizes in both sexes.
- It successfully detected full FMR1 gene mutations in males.
- The method demonstrated high sample throughput.
Conclusions:
- This fluorescent PCR assay is a valuable tool for initial screening of Fragile X syndrome in males with intellectual disability.
- It offers a faster and more efficient alternative to traditional methods.
- Southern blot may still be needed for assessing methylation status in large mutated alleles.
