Comparison of repeat-flanking PCR and TP-PCR melt peaks.

<p>Melt peaks of normal and HD-affected samples are plotted in blue and red lines, respectively, while the p<i>HTT</i>(CAG)₂₆ and p<i>HTT</i>(CAG)₃₃ melt peaks are in black lines. Samples were assayed in triplicate. <b>Top</b>, repeat-flanking PCR MCA of the normal sample produces a single melt peak with a T_m in the normal range, whereas the HD-affected samples produce a dominant melt peak with T_m in the normal range and second melt peak with T_m in the expanded range. Melt peak height of the expanded allele decreases with increasing repeat length, risking an absent expanded allele peak if expansion is very large, with only the normal allele peak present. <b>Bottom</b>, TP-PCR MCA produces a single distinct melt peak in every sample regardless of disease status or length of repeat. The melt peak T_m relative to the threshold temperatures of p<i>HTT</i>(CAG)₂₆ and p<i>HTT</i>(CAG)₃₃ effectively determine normal or HD-affected status of each sample.