Chromosomes condense in three timed chemical waves during cell division, study shows

DNA does not float freely within the cell. Instead, it wraps around histone proteins to form structures called nucleosomes. These histones carry numerous chemical modifications that act as molecular signals, controlling the degree of DNA encapsulation and which genes are active. During cell division, this DNA-histone complex, called chromatin, must be further condensed into compact rod-shaped chromosomes. Histone modifications play a key role in this process: they change significantly during condensation and regulate chromatin conversion.