Friedrich Miescher was the first to identify DNA, in 1869.

Direct answer

  • Out of the names you listed (Rosalind Franklin, Erwin Chargaff, Friedrich Miescher, James Watson), Friedrich Miescher is credited with first identifying DNA as a distinct substance, which he called “nuclein,” in the late 1860s.

How the others fit in

  • Rosalind Franklin produced key X‑ray diffraction images (like “Photo 51”) that revealed DNA’s helical nature and were essential for working out its structure.
  • Erwin Chargaff discovered the base‑pairing regularities (A = T and C = G), now known as Chargaff’s rules, which were crucial clues to the double‑helix model.
  • James Watson (with Francis Crick) proposed the double‑helix structural model of DNA in 1953, building on Franklin’s data and Chargaff’s rules, and became widely associated with the “discovery of the structure of DNA.”

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