Genes that escape XCI have significantly lower AIs than genes that are subject to XCI. (A) The degree of skewing of XCI varies between sample sets. To determine the degree of skewing all genes from the subject training set were examined (minimum of two probes per gene) and the average AI per gene determined (only probes with a total cDNA greater than the sample set threshold; Additional file 2). The thick black line shows the AI at which 99.5% of autosomal genes are found. Females with an average AI from the subject training set above this threshold were classified as the most highly skewed females in each population (group 1, squares), females below this threshold were classified as either group 2 (circles) or group R (triangles). (B) Examining group 1 females only, genes from the escape training set (green) have a significantly (P-value <2.2 e-16) lower genic AI than genes from the subject training set (red). Genes located in the Xp pseudoautosomal region (PAR1) are shown as triangles while circles represent non-PAR1 genes.
Cotton et al. Genome Biology 2013 14:R122 doi:10.1186/gb-2013-14-11-r122