During replication, parental nucleosomes are recycled and deposited onto the two daughter strands. In the random segregation model, the parent histone octamers (red cylinders) are intact and pass to the two daughter strands in a random manner. Newly assembled nucleosomes (grey cylinders) fill in the gaps not occupied by the parental octamers and histone-modifying enzymes copy the parental histone modifications (e.g. Acetylated groups, Ac) to newly assembled nucleosomes. In the semi-conservative model, the parent histone octamers split in half and are equally distributed among the two daughter strands (red halves). Nucleosome assembly complexes then deposit newly synthesized histones to complement the existing halves of the nucleosomes (grey halves) present on the daughter strands. In this case, histone modifying enzymes would copy the modifications (e.g. Ac) to the new half of the nucleosomes from the old half (symbolized by the green arrows).