|MadSci Network: Science History|
Hello! There were three models for how DNA could replicate: A conservative model where the parental double helix remained intact and a completely new daughter double strand was formed, the semi-conservative which you mentioned, and dispersive in which there is some random combination of parental and daughter strands. These were just three theories proposed, and no model of conservative replication was postulated. It was the experiments of Messelson and Stahl that proved DNA replication was semi-conservative (http://www.district87.org/biology87/APBiology/notes/Mol_Gen/Mol_Gen.htm or http://www.stolaf.edu/people/chial/lecture27_files/sld017.htm). It wasn't until Watson and Crick determined the structure of DNA that the mechanism of unzipping the DNA and copying each strand was realized (http://www.stolaf.edu/people/chial/lecture27_files/sld014.htm). I hope this answers your question. Good luck, Sarah Tegen
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