Length determination of nucleic acid repeat sequences by discontinuous primer extension

[Subject] Offer a method exact [for determining the number of the repeating units which form the repetitive domain of a nucleic acid reiterated sequence], and reproducible. [Solution means] The method for determining the number of the repeating units in the repetitive domain of target nucleic acid is indicated. This method includes a discontinuous primer reaction and a primer is elongated in each increase corresponding to a single repeating unit here. When a detection process is performed after each increase in primer extension and a primer is elongated to a quantity equal to the sum total of the length of a repetitive domain, the abnormal conditions in a signal are detected. By calculating the number of the increases in each primer extension needed for causing the abnormal conditions of a signal, the number of the repeating units which make a repetitive domain is determined. [Selection figure] Nothing