DNA molecular model, 1953.
© Science Museum / Science & Society Picture Library
Detail. Francis Crick (b 1916) and James Dewey Watson (b 1928) made the original DNA model in 1953 while working in the Medical Research Council Unit at the Cavendish Laboratory in Cambridge. They discovered that DNA (deoxyribonucleic acid) is made up of a double helix (ie two strands) of phosphate 'backbones' joined by complementary sequences of base pairs (units of genetic information). To replicate, the two chains unwind and act as templates.