BIO 315H Lecture Notes - Lecture 2: Matthew Meselson, Franklin Stahl, Isotopes Of Nitrogen
Document Summary
Nucleotides can only be added to the 3" end. Hydrogen bond - hydrogen bonded to electronegative atom (oxygen) Matthew meselson and franklin stahl designed a classic experiment to distinguish the three possible hypothetical models. Label dna with nitrogen 14n (the most common) and 15n(heavier) Cesium chloride (separate by weight) heavier stuff goes to bottom and lighter stuff goes to top. Uv light to show where dna is in the tube. Used nitrogen because it is found in the bases and can be used to label the bases. If dna migrates halfway between light and heavy: it is double stranded and one strand is heavy and one is light. Disproves conservative because it does not have 2 bands and conservative would have two bands. After many replications you start to add more and more 14n so it becomes lighter. Muscles cells, nerve cells, gametes do not replicate. Skin cells, digestive system cells replicate a lot.
