DNA replication in eukaryotes is much more complex than in prokaryotes while there are various same aspects. The Eukaryotic cells can only initiate DNA replication at a particular point in the cell cycle, the starting of S phase. The DNA replication in eukaryotes happens only in the S phase of the cell cycle. Furthermore, pre-initiation happens in the G1 phase. Thus, pre-initiation and activation needs two very several intra-cellular contexts to follow each other in the right order making it very unlikely which replication will take place more than once per cell cycle.
With the Due to the sheer size of chromosomes in eukaryotes and eukaryotic chromosomes hold multiple origins of replication. Some origins are well characterized, like the ARS (autonomously replicating sequences) of yeast although other eukaryotic origins, mainly those in metazoan which can be found in spans of thousands of basepairs. Though, the initiation and assembly of replicaton is similar in both the metazoa and protozoa.