Which of the following techniques was most helpful to Watson and Crick in developing their model for the structure of DNA?

• A. Radioactive labeling
• B. Electrophoresis
• C. Cloned DNA
• D. Transgenic animals
• E. X-ray crystallography

Answer: (E)

Verified step by step guidance

1. Understand the historical context: Watson and Crick were working on discovering the structure of DNA in the early 1950s. At that time, several techniques were being developed and used to study biological molecules.
2. Learn about X-ray crystallography: This technique involves directing X-rays at a crystallized sample of a molecule. The X-rays are scattered by the atoms in the crystal, creating a diffraction pattern that can be captured on film or a detector.
3. Explore how X-ray crystallography contributed to the discovery: The diffraction patterns obtained from X-ray crystallography provide information about the three-dimensional arrangement of atoms within a molecule. For DNA, this was crucial in revealing the helical structure.
4. Recognize the role of Rosalind Franklin: Her X-ray diffraction images of DNA, particularly Photo 51, were critical in helping Watson and Crick deduce the double helix structure. Her work provided key insights into the dimensions and shape of the DNA molecule.
5. Connect the technique to the model development: Watson and Crick used the data from X-ray crystallography to build a physical model of DNA, incorporating the helical structure and complementary base pairing, which explained how genetic information is stored and replicated.