Half of the strand is the old DNA, half is the newly replicated strand.
Process:
DNA helicase breaks open H bonds separating the two strands of DNA
Free RNA nucleotide bases bind specifically to their complementary bases
Phosphodiester backbone created by DNA polymerase in a series of condensation reactions
two identical molecules of DNA are formed
Evidence for semi-conservative replication
All DNA bases contain nitrogen, which has two forms (lighter 14N and isotope 15N which is heavier
Bacteria incorporate nitrogen from their growing medium into any new DNA they make
Centrifuged extracted DNA and found by analysing test tubes that half new and half old DNA was present (as lighter 14N would sit higher than isotope 15N
