Nucleic acids - DNA replication

4) free activated dna nucleotides in nucleus are attracted to their complementary exposed base (A-T and C-G) and link by hydrogen bonds
5) dna polymerase catalyses the condensation reactions between deoxyribose and phosphates of adjacent nucleotides to form a sugar phosphatebackbone

1) They chose bacteria as replicate every 20 minutes
2) 2 isotopes of nitrogen (N15 and N14) in growth medium (food for bacteria) so they could identify which were new nucleotides and which were in original DNA molecule. The N used to make the nitrogenous bases
3) N15 (labelled N) is a slightly heavier atom than N14
4) The bases and the way they pair not affected by different isotope

5) A density gradient can be produced by centrifuging Caesium Chloride (CsCl) at very high speed overnight
6) If DNA is also placed in tube it will remain intact and settle at point where it’s density equals that of the CsCl