Rosalind Franklin contributed to understanding DNA structure by:

Rosalind Franklin contributed to understanding DNA structure by:

• A. James Watson
• B. Francis Crick
• C. Rosalind Franklin
• D. Linus Pauling

Answer: (C)

Understanding DNA’s shape comes from the evidence scientists gathered about its form. Rosalind Franklin used X-ray diffraction to image DNA fibers, producing clear patterns that reveal not just that DNA is helical, but specific details about its dimensions. Her images, especially the one known as Photo 51, showed an X-shaped pattern indicating a regular helix, and they helped scientists estimate a uniform diameter of about 2 nanometers and a repeating base-pair spacing of roughly 3.4 angstroms per rung. Those concrete measurements and the visible helicity provided crucial, concrete evidence that DNA is a double helix with specific geometry, which then guided the building of the correct model. So the contribution is that Franklin’s diffraction data gave the essential structural evidence—the helical nature and dimensions—that made the double-helix model plausible. While Watson and Crick later constructed the actual model using that and other data, Franklin’s experimental results were the key input that pointed to the helical structure and informed the correct arrangement of the two strands. Linus Pauling proposed an incorrect triple-helix idea, so his model did not match the true DNA structure.

Understanding DNA’s shape comes from the evidence scientists gathered about its form. Rosalind Franklin used X-ray diffraction to image DNA fibers, producing clear patterns that reveal not just that DNA is helical, but specific details about its dimensions. Her images, especially the one known as Photo 51, showed an X-shaped pattern indicating a regular helix, and they helped scientists estimate a uniform diameter of about 2 nanometers and a repeating base-pair spacing of roughly 3.4 angstroms per rung. Those concrete measurements and the visible helicity provided crucial, concrete evidence that DNA is a double helix with specific geometry, which then guided the building of the correct model.

So the contribution is that Franklin’s diffraction data gave the essential structural evidence—the helical nature and dimensions—that made the double-helix model plausible. While Watson and Crick later constructed the actual model using that and other data, Franklin’s experimental results were the key input that pointed to the helical structure and informed the correct arrangement of the two strands. Linus Pauling proposed an incorrect triple-helix idea, so his model did not match the true DNA structure.