CTAG1A and CTAG1B (both originally known as NY-ESO-1 before the duplication was discovered) are located in a duplicated region of chromosome X causing two approximately 35kb dark-by-MAPQ regions (Fig. 3e.i) and are primarily expressed in specific cell types within the testes and in several types of cancer (e.g. breast cancer, leukemia, etc.)making it a potential therapeutic target [19–23]. This evidence concerns the gene CTAG1A and breast cancer.