Mechanism of nuclear DNA replication in radicles of germinating cotton

The mechanism of nuclear DNA replication in radicles of germinating cotton (Gossypium barbadense) was investigated. Pulse-labeling with [³H]thymidine indicates that replication intermediates are of small molecular weight (4-10S) and behave as if single-stranded. Prolonged labeling indicates that intermediates are of discrete size, suggesting a mechanism of discontinuous replication. Electron microscopy of nuclear DNA demonstrates a complex architecture which may include “eye forms” and “forks” similar to those reported in prokaryotes and animal systems. The possible universality of DNA replication mechanisms is discussed.