Chromosomal distribution of tissue-biased genes. Distribution of tissue-specific genes in the X chromosome and autosomes of D. melanogaster. (A) By an alternative way to present the data found in Figure 3B, we observed that only accessory gland-, mid-gut-, and testis-specific genes are significantly under-represented on the X chromosome. (B) The same chromosomal distribution analysis for tissue-specific genes was performed only with genes that are not testis- or ovary-biased expressed, that is, have the same expression in testis and ovaries. No differential chromosomal distribution is found for any of the analyzed dataset of tissue-specific genes. Significant deviations (Fisher's exact test or Chi-square with Yates correction) are indicated for tissue-specific datasets with minimal tissue-to-tissue signal ratio larger than two-fold (***P < 0.001; **P < 0.01, *P < 0.05).