(i) Conservative mode
This hypothesis states that during replication both the strands of the DNA remains with the parent cell and the newly synthesized two strands of DNA is retained by the daughter cell. However this hypothesis is not accepted anymore.

(ii) Dispersive mode
 Replication would involve fragmentation of the parent DNA strands and intermixing with the newly synthesized strands. However this model is discarded since it not proved experimentally.
(iii) Semi conservative mode
Here the replication process of a parent DNA double helix results in two hybrid DNAs. Here each of the daughter DNA double helices retains a parent strand and a newly synthesized strand. The experiments of Mathew Messelson and Franklin W. Stall using isotopically labeled DNA and a form of isopycnic density gradient centrifugation has proved the semi conservative mode of replication in the DNA.