This isotope of nitrogen is heavier than the naturally abundant 14 N isotope. They then transferred the bugs to a media containing only the 14 N isotope and looked at the distribution of the two isotopes with each successive generation. They did this with density gradient ultracentrifugation. The molecular mechanism of DNA replication was worked out by Arthur Kornberg. They isolated the enzyme DNA polymerase I. Replication involves the interplay of more than twenty proteins.
Replication requires activated precursors.
The dinucleotide triphosphates. Elongation of DNA occurs in the 5' to 3' direction. I is a template directed enzyme. DNA can be melted Exposure to heat, acid or alkali can cause the DNA strands to separate. It contains a 2' hydroxyl group on the ribose sugar.