In prokaryotes, most or all of an organism's genetic information is stored in one long, circular DNA ring instead of multiple chromosomes of DNA strings with unconnected ends as in eukaryotes. These rings are replicated in a very similar manner to eukaryotic DNA, the only real difference being that here only two replication forks are used. While eukaryotes had many replication sites in action at once, prokaryotes replicate so quickly that only two, one working in each direction around the ring, are needed. Hope that helps..