(A) Drosophila male GSC: sister chromatids are either enriched with old histone (green) or new histone (red) H3 and H4. Histone segregates asymmetrically into the daughter cells; a representative example of global histone asymmetry. Also, CENP-A segregates asymmetrically into daughter cell, represent centromere epigenetic asymmetry and non-random sister chromatids segregation. (B) Drosophila female GSC: sister chromatids are overall carrying a symmetric level of old and new histone. However, a local asymmetry between old and new histone can be seen at stem cell maintenance genes and differentiation gene loci; a representative example of gene-specific histone asymmetry (also found in mouse embryonic stem cells that are induced to undergo ACD). Interestingly, despite of the overall symmetric histone segregation, CENP-A segregates asymmetrically into daughter cell, suggesting sister chromatids still carry epigenetic information differentially and segregate non-randomly.