In the past year, genetic studies have provided a detailed understanding of the DNA sequence elements that constitute Saccharomyces cerevisiae origins of DNA replication and have identified larger DNA domains that direct DNA replication in both Schizosaccharomyces pombe and human cells. In vivo studies of the proteins associated with S. cerevisiae origins of DNA replication indicate that there are dynamic changes in origin chromatin structure during the cell cycle and suggest that the Cdc7 protein kinase is among the associated proteins.