meelson and stahl's evidence

• 1. two samples of bacteria grown - one in broth of light nitrogen, one in broth of heavy nitrogen. as they reproduced, they took up nitrogen to make nucleotides, so it was added to their DNA
• 2. sample of DNA taken from each batch, and spun in centrifuge. sample from heavy nitrogen settled further down the tube than sample from light nitrogen
• 3. bacteria from heavy nitrogen placed in broth with only light nitrogen. left for one round of DNA replication then spun in centrifuge
• 4. settled in the middle, proving semi-conservative replication, as contained both heavy and light nitrogen