The human homolog, hsSgo1, associates with centromeres during prophase and disappears when anaphase starts. Instead, they remain tightly associated with the centromeres of non-disjoined sister chromatids. Regional centromeres contain large amounts of DNA and are often packaged into heterochromatin. Though Aurora B is enriched at centromeres, it localizes diffusely to all chromatin. The NORs are "sandwiched" between the repetitive, heterochromatic DNA sequences of the centromeres and telomeres. A dicentric chromosome is an abnormal chromosome with two centromeres. During meiosis I, the centromeres are not duplicated. The heterochromatic regions are the areas near the centromeres and nucleolar organizers. The best characterised point centromeres are those of the budding yeast, "Saccharomyces cerevisiae". The recombination needs to occur between the centromeres of the adjacent gene. In Drosophila, Islands of retroelements are major components of the centromeres. In regional centromeres, DNA sequences contribute to but do not define function. This protein also associates with centromeres in G2 phase. Point centromeres are smaller and more compact. The lengths of the three centromeres were found to be 34, 65, and 110 kb.