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. 2021 Feb 8;22(4):1689. doi: 10.3390/ijms22041689

Figure 3.

Figure 3

Known polymorphisms adjacent to or within the CAG repeat tract. The AmplideX PCR/CE HTT Kit accurately genotypes templates with known polymorphisms adjacent to or within the CAG repeat tract. (A) Template with 19 repeats showing the expected CE electropherogram and corresponding genotype for the relevant portion of the HTT reference sequence. (B) DNA with two SNPs (rs473915 A>G and rs76533208 A>G) interrupting the 12-bp spacer region (shown in italics) is successfully amplified to produce the expected 19 CAG result. (C,D) PCR/CE genotyping of each SNP (rs473915 or rs76533208, respectively) results in the correct 19 CAG call. (E) A CAA frameshift (rs779781803) within the repeat sequence shows a repeat-primed amplification pattern and a terminal peak corresponding to 20 CAG, rather than 19 CAG, due to the mobility shift caused by the triplet interruption. Note that the CAA interruption causes a signal “dip” in the repeat-primed pattern; this dip flags result as suspicious for unexpected sequence variation.