semiconservative replication model

Semiconservative replicationclick for a larger image
Fig. 281 Semiconservative replication. Meselson and Stahl's results.
Semiconservative replicationclick for a larger image
Fig. 280 Semiconservative replication . DNA duplication.

semiconservative replication model

a model of DNA duplication in which each strand of the double-stranded DNA serves as a template for synthesis of a new strand. Thus each new (daughter) duplex of DNA contains one POLYNUCLEOTIDE CHAIN from an original (parental) molecule and one chain newly synthesized from individual NUCLEOTIDES. Hence one strand is conserved in each double-stranded DNA molecule, which is therefore described as semiconserved. See Fig. 280 . That such a model could be tested experimentally was shown by Matthew Meselson and F. Stahl in 1958, using radioactively labelled DNA of E. coli. They employed two ISOTOPES of nitrogen of different weight 14N (light) and 15N (heavy), the two types being distinguishable by DIFFERENTIAL CENTRIFUGATION.

The semiconservative replication model has superseded the CONSERVATIVE REPLICATION MODEL.