Temporal genetic mapping in the blue-green alga Anacystis nidulans using ethyl methanesulphonate

Cultures of the blue-green alga Anacytis nidulans were synchronized with respect to DNA synthesis as well as cell division. Application of ethyl methanesulphonate at different stages of replication resulted in a peak of mutation frequency for different genetic markers; this peak can be accounted for in terms of the involvement of repair processes. A temporal map of 19 markers has been constructed by this method. Comparison of gene position obtained by temporal mapping indicates that either bidirectional replication or unidirectional replication from more than one origin occurs.