Proofs of the Double Helix model for DNA

The prediction of replication appears to be the most significant and the most easily tested hypothesis

1958 Matthew Meselson and Fanklin Stahl proposed and tested 3 models for DNA replication.

They grew bacterial cells in media made heavy nitrogen (15N) and then transfered these cells to media with light or natural nitrogen(14N). The results are shown in Figure 23-3 (Woolf).

• After one round of replication the Conservative Model is proven false
• After a second round of replication the Dispersive Model is proven false.
• Thus by the scientific method the Semi-Conservative Model is assumed true.

Let us review these results.

Please note that this is a beautiful experiment that rules out all reasonable hypotheses.

Herbert Taylor did essentially the same experiment at the same time (1958) in beans.

Today we would use 5-bromouracil for both of these experiments.
This is the theory.
This is the actual .

Text iGenetics by Peter J. Russell

This web site is provided for instruction in Botany and Zoology 342

by Kenneth G. Wilson,
Professor of Botany
Miami University
wilsonkg@muohio.edu