Who are credited with developing the double helix model of DNA?

• A. Darwin and Wallace
• B. Miescher and Chargaff
• C. Franklin and Wilkins
• D. Watson and Crick

Answer: (D)

The main idea here is identifying who proposed the actual three-dimensional structure of DNA. James Watson and Francis Crick proposed the double helix model in 1953, describing DNA as two long strands wound around each other with a sugar–phosphate backbone on the outside and bases paired inside the helix. Their model incorporated Chargaff’s rule that adenine pairs with thymine and guanine pairs with cytosine, which explains how the two strands can fit together in a way that allows accurate replication. They also used Rosalind Franklin and Maurice Wilkins’ X-ray diffraction data that indicated DNA is helical and has regular dimensions, helping to shape the final structure they proposed.

Other scientists contributed important pieces to DNA science, but Watson and Crick are credited with developing the actual double-helix model. Darwin and Wallace are known for natural selection, Miescher identified the substance that would become DNA, Chargaff established base-pair rules, and Franklin and Wilkins provided key experimental data that guided the model. The combination of a concrete structural proposal and a mechanism for replication is what solidified Watson and Crick’s role in this discovery.