Non-DNA linkers

There are a number of different reasons why non-DNA linkers have been considered necessary to hold DNA molecules in tandem arrangement in chromosomes. The most relevant of these to the regulation of DNA synthesis are as follows the presumption that replication units of DNA within a sin e chromosome cannot be directly connected to one another without interruption of the DNA double helix the need for a mechanism to relieve torsion of the DNA molecule, torsion developed in connection with semiconservative replication. The latter proposal that non-DNA linkers mi t serve to allow rotation of the DNA double helix during semiconservative replication is no longer considered valid since it has been repeatedly demonstrated that a single-stranded break in a DNA double helix allows the intact chain to serve as a swivel and release torsion within the molecule (Vlnograd and Lebowitz, 1966). 

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