Which scientists are credited with the discovery that DNA has a double-helix structure using X-ray data?

• A. Crick and Watson
• B. Franklin
• C. Hershey and Chase
• D. Meselson and Stahl

Answer: (A)

The idea being tested is how X-ray data informed the discovery of DNA’s double-helix structure. X-ray diffraction patterns provided crucial clues about DNA’s shape and dimensions, notably that it is a regular, helical molecule with specific spacing between base pairs. Rosalind Franklin’s X-ray images supplied the clear evidence of a helix and helped establish the geometry, while Chargaff’s rules about base pairing guided how the two strands fit together.

Watson and Crick are credited with the double-helix model because they took that X-ray information and, together with Chargaff’s rules, built and published the correct helical structure in 1953. Their model explained how DNA could store genetic information and be replicated, tying together the structural clues from X-ray data into a coherent, workable framework.

The other scientists contributed in important ways that aren’t about proposing the final helical structure from X-ray data: Franklin provided the essential X-ray diffraction visuals; Hershey and Chase showed that DNA is genetic material through experiments with bacteriophages; Meselson and Stahl demonstrated semi-conservative replication.