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James Watson and Francis Crick discover the double helix structure of DNA

Francis Crick and James Watson

James Watson and Francis Crick discover the double helix structure of DNA

When Francis Crick and James Watson modeled the structure of DNA, they used paper cutouts of the bases (A, C, G, T) and metal scraps from a machine shop. Their model represented DNA as a double helix, with sugars and phosphates forming the outer strands of the helix and the bases pointing into the center. Hydrogen bonds connect the bases, pairing A–T and C–G; and the two strands of the helix are parallel but oriented in opposite directions. Their 1953 paper notes that the model “immediately suggests a possible copying mechanism for the genetic material.”
1953