Watson and Crick, James Watson and Francis Crick suspected DNA to be a helix in the 1950s. They made models from scraps of metal connected by suitably angled bonds of wire.
Erwin chargaff- his first rule States: the amounts of thymine and adenine are identical, and so are the amounts cytosine and guanine. Chargaffs second rule States: DNA of different species has different amounts of adenine and guanine
Before division, a cell copies its chromosomes two make two sets. The process by which a cell copies its DNA is called DNA replication. Before DNA replication, a chromosome consists of one molecule of DNA (one double helix). As replication begins, enzymes break the hydrogen Bonds that hold the double helix together. Another enzyme constructs primers: short, single strands of nucleotides