Machado–Joseph disease (MJD) is a rare inherited neuromuscular disease that is caused by a mutation in the gene ATXN3. The protein encoded by this gene contains "CAG" repeats in the coding region, and the expansion of these repeats from the normal 12-44 to 52-86 is the most common cause of the disease.

It is well known that amplification of repetitive DNA by PCR is prone to errors, mainly caused by misalignment/slippage of the polymerase during the elongation phase.

Does anyone know if there exists a specialized PCR protocol or polymerase that could accurately amplify the repetitive region of ATXN3 such that one could then use gel electrophoresis or Sanger sequencing to approximate the number of CAG repeats?


1 Answer 1


This paper describes an allele-specific PCR protocol to detect CAG repeat expansion in MJD patients:

Maciel P, Costa MDC, Ferro A, et al. Improvement in the Molecular Diagnosis of Machado-Joseph Disease. Arch Neurol. 2001;58(11):1821–1827.


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