DNA sequencing 1953, James Watson and Francis Crick put forward their double-helix model of DNA, based on crystallized X-ray structures being studied by Rosalind Franklin – and without crediting her. According to the model, DNA is composed of two strands of nucleotides coiled around each other, linked together by hydrogen bonds and running in opposite directions. Each strand is composed of four complementary nucleotides – adenine (A), cytosine (C), guanine (G) and thymine (T) – with an A on one strand always paired with T on the other, and C always paired with G. They proposed such a structure allowed each strand
Timeline of United States discoveries chloride 1936 Elliptical galaxies 1936 Muons 1936 Vitamin E 1936 Sodium thiopental 1937 Niacin 1937 Electron capture 1938 Fluropolymers 1938 Animal echolocation 1938 Carme 1938 Lysithea 1940 Plutonium 1942 Cyanoacrylate 1943 Streptomycin 1944 Americium 1944 Curium 1946 Cloud seeding 1948 Warfarin 1948 Miranda 1948 Serotonin 1948 Tetracycline 1949 Nereid 1949 Berkelium 1950 Californium 1951 Barium stars 1951 Ananke 1952 Polio vaccine 1952 Einsteinium 1952 Rapid eye movement 1953 DNA structure In 1953, based on X-ray diffraction images and the information that the bases were paired, James D. Watson along with Francis Crick co-discovered what is now widely accepted as the