sYG1 is a multi-copy gene on the Y. Copy number determination using digital droplet PCR designed to detect both sYG1 and AsA-bbx indicates two autosomal AsA-bbx copies (seen in females) and six-to-nine copies of sYG1 in males (8 to 11 copies minus the two autosomal copies). Since we know that sYG1 hybridizes to the Y in FISH, we can infer that the extra copies of sYG1 in males is due to the fact that there are many copies of sYG1 on the Y. Digital PCR partitions a sample into as many as 20,000 individual droplets and uses TaqMan chemistry with fluorescently labelled probes to accurately determine the copy-number of genes. An autosomal reference gene (sequence provided in Additional file 3) was set as having two copies per diploid genome. The copy number of sYG1/AsA-bbx was determined by comparison to the autosomal reference. Error bars represent poisson error.
Hall et al. BMC Genomics 2013 14:273 doi:10.1186/1471-2164-14-273