In Drosophila there is a paucity of male-biased genes on the X chromosome, while there is a slight enrichment of female-biased genes on this chromosome (Parisi et al. 2003; Ranz et al. 2003). The figures below show the distribution of sex-biased genes on the X chromosome and the autosomes. Sex-biased genes were classified using both a FDR of 5% and a 2-fold cutoff.