Which scientist used X-ray diffraction to study the DNA molecule?

• A. James Watson
• B. Francis Crick
• C. Rosalind Franklin
• D. Erwin Chargaff

Answer: (C)

X-ray diffraction analyzes how X-rays scatter off a sample to reveal its shape and dimensions. For DNA, this technique can show whether the molecule forms a helix, its diameter, and how the subunits stack along the axis. Rosalind Franklin applied this method to DNA fibers and produced high-quality diffraction patterns that clearly indicated a helical structure with a regular width. Those patterns provided essential, concrete constraints about DNA’s architecture that helped others assemble the correct model of a double helix. Watson and Crick used that structural information, along with Chargaff’s rules about base pairing, to finalize their model. Chargaff’s work explained which bases pair together but did not provide the X-ray images of DNA. In short, Rosalind Franklin used X-ray diffraction to study the DNA molecule.