Biob11-l12: dna replication i general aspects and enzymology. Dna is a double stra(cid:374)ded helix (cid:894)chargaff(cid:859)s rules: [a]=[t], [c]=[g](cid:895) What they postulated: helix = anti parallel ; each strand = template for replication of a new strand. Each strand serves as a template for the formation for the complementary strand. Energy and time efficient, less prone to errors. Used e. coli to investigate the mechanism of replication, employed a density label, n15, or heavy nitrogen (supplied as 15nh4cl) Utilizes a dense medium (e. g. 6m cscl) and particles sediment until they reach their buoyant density (equilibrium) Dispersive: progressive enrichment for n14 strands (lighter) as more new n14 are added into the dna only one band. Conservative: original strands together no hybrids found, only n14/14 and n15/15. Increase in n14/14 due to further replication in further generation. Semiconservative: hybrid on first generation hybrid and n14/14 bands after. After one round of replication all molecules sediment at the hybrid (n14/15) density.