Related: Biological Science MOC, BCMB 412 Advanced Molecular Biology and Genomics
Summary
Half of the original DNA is conserved in each new strand.
When replicating, double stranded DNA will dissociate to individual strands (not all at once, but in segments) on which DNA polymerase synthesizes complements, generating two identical strands of DNA.
Since each complement is synthesized on an individual strand of the original DNA, the two new DNA molecules will each contain an individual strand from the original (parent) and a newly synthesized complement to the original.
photo from [Modes of DNA Replication](https://www.mun.ca/biology/scarr/iGen3_03-01.html)
The Meselson-Stahl experiment demonstrated DNA’s semiconservative replication by tracking nitrogen isotopes through generations of DNA replication.
- When heavy DNA (containing 15N) was allowed to replicate in media with light nitrogen (14N), the first generation produced a single band of intermediate density DNA, containing one heavy and one light strand.
- The second generation produced two distinct bands: one intermediate-density band and one light-density band, as expected when each parent strand templates a new light strand.
What the experiment would have shown if it wasn’t semi-conservative
- If conservative: would show separate heavy and light bands in both generations
- If dispersive: would show progressively lighter single bands