The heterochromatic regions are the areas near the centromeres and nucleolar organizers. The NORs are "sandwiched" between the repetitive, heterochromatic DNA sequences of the centromeres and telomeres. Both RNAi and an exosome-dependent RNA degradation process contribute to heterochromatic gene silencing. The inactive X chromosome is packed via DNA condensation into a heterochromatic Barr body formation. Pol V is involved in siRNA-directed DNA methylation pathway which leads to heterochromatic silencing. Ectopically expressed BAHD1 colocalizes with the heterochromatic inactive X chromosome (Xi). Chromosomes that have HR experience separation of the heterochromatic regions during metaphase. Fibroblast nucleus is typically euchromatic, but TC nucleus is mostly heterochromatic. Approximately 5% of the genome is heterochromatic. Mabel was noticeable for having heterochromatic eyes (one blue and one brown) and distinctive ears. Xayide's most striking physical feature are her heterochromatic red and green eyes. Heterochromatic regions of chromosomes tend to associate together in a specific compartment of the nucleus. Also, great variety is seen in the Aussie's eye color, and they are often heterochromatic. It also defines the boundaries between active and heterochromatic DNA.