Supercoiled loops and the organization of replication and transcription in eukaryotes

The nuclear DNA of eukaryotes is organized into a series of loops each topologically anchored by elements of the nuclear matrix. Evidence is reviewed which indicates that the anchorage points of the loops are formed by transcriptionally active genes and that individual loops function as replicons. The data suggests a specific model for coupling of DNA replication and transcription in eukaryotes.