Triplet-Repeat Primed PCR and Capillary Electrophoresis for Characterizing the Fragile X Mental Retardation 1 CGG Repeat Hyperexpansions

  • Indhu-Shree Rajan-Babu
  • Samuel S. ChongEmail author
Part of the Methods in Molecular Biology book series (MIMB, volume 1972)


Fragile X mental retardation 1 (FMR1) CGG repeat expansions cause fragile X syndrome—the leading monogenic form of intellectual disability—and increase the risk for fragile X-associated tremor ataxia syndrome and fragile X-associated primary ovarian insufficiency. Southern blot (SB) analysis is the current gold standard test for FMR1 molecular diagnosis. Several polymerase chain reaction (PCR)-based methods are now available for sizing FMR1 CGG repeat expansions. These methods offer higher diagnostic sensitivity and specificity compared to SB analysis, significantly reduce the turnaround time and increase throughput. In this chapter, we describe a triplet-repeat primed PCR protocol that employs capillary electrophoresis to resolve the derived amplicon products, enabling precise determination of the FMR1 genotypes in both males and females and characterization of the CGG repeat structure.

Key words

Capillary electrophoresis TP-PCR FMR1 Fragile X syndrome Repeat expansion FXTAS FXPOI 


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Pediatrics, Yong Loo Lin School of MedicineNational University of SingaporeSingaporeSingapore
  2. 2.Department of Medical GeneticsThe University of British ColumbiaVancouverCanada
  3. 3.Khoo Teck Puat—National University Children’s Medical InstituteNational University Health SystemSingaporeSingapore
  4. 4.Department of Laboratory MedicineNational University HospitalSingaporeSingapore

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