An assay of gene copy number and its application based on heteroduplex products

The aim of this study was to set up a simple and efficient method for detecting gene copy number, based on heteroduplex products from single-tube PCR/DHPLC. Single-nucleotide polymorphisms (SNPs) on the α-globin gene and chromosome 21 were used as examples. And the formula for quantitative calculation of gene copy number was deduced—based on the peak heights of homoduplexes and heteroduplexes on the DHPLC pattern. 27 samples (14 normal DNA and 13 cases of trisomy-21) were assessed with this method, and 160 samples (48 normal DNA and 112 α-thalassemia samples) were assessed with this method combined with a duplex PCR/DHPLC. Results for 184 of 187 cases were concordant with the known genotypes; three cases of trisomy-21 could not be detected because the target SNPs were homozygous. In conclusion, quantitative assessment of heteroduplex products from single-tube PCR/DHPLC is simple and rapid, and can be used to detect α-thalassemia gene deletions (α− 3.7, α− 4.2) and trisomy-21.

Research Highlights
► Gene copy number can be detected by the studied assay: single-tube PCR/DHPLC.
► This assay can be used to identify trisomy 21.
► Types of α-thalassemia can be detected by the assay combined with a duplex PCR/DHPLC.