Replicating circular DNA molecules in yeast

The yeast Saccharomyces cerevisiae contains a class of small circular DNA molecules, approximately 2 μm in contour length (Sinclair et al., 1967). In this report, it is shown that these molecules replicate as double-branched circles, similar to those observed during replication of the bacteriophage λ and Escherichia coli chromosomes. A normal rate of replication of these DNA circles requires the function of a nuclear gene, cdc 8.