[Structural arrangement of chromatin (author's transl)].

Recent observations and hypotheses on the structure of chromatin are reviewed. Elementary "subunit" for higher structural orders is the nucleosome, consisting of a histone octamer and doublehelical DNA wrapped around it. During the last years details of the nucleosomal structure could be deduced down to a resolution of 2 nm. In the chromatin fiber, built up by (mono-)nucleosomes, the superhelical DNA has a tertiary structure, from which structures of still higher order (quaternary structure of DNA) can be formed. The correlation of these structures to the terms euchromatin and heterochromatin are discussed. Finally, some functional aspects, especially transcription and replication, are discussed in view of the new knowledge of chromatin structure.