1. X-ray Diffraction:

* This is the most famous and impactful technique used by Rosalind Franklin and Maurice Wilkins.

* X-rays are beamed onto DNA fibers, and the diffraction pattern (how the X-rays scatter) is analyzed.

* The pattern revealed a repeating helical structure, with the crucial information needed to decipher the double helix model.

2. Electron Microscopy:

* Electron microscopy offers a more direct visual representation of the DNA molecule.

* It uses a beam of electrons to illuminate the sample, providing high-resolution images.

* Electron micrographs show the DNA molecule as a long, twisted ladder-like structure, confirming the helical arrangement.

3. Circular Dichroism (CD) Spectroscopy:

* This technique measures the difference in absorption of left-handed and right-handed circularly polarized light by molecules.

* DNA's double helix exhibits a characteristic CD spectrum, indicating the helical structure.

4. Nuclear Magnetic Resonance (NMR) Spectroscopy:

* NMR spectroscopy analyzes the magnetic properties of atomic nuclei.

* By examining the NMR spectrum of DNA, scientists can determine the arrangement and relative positions of atoms within the molecule, confirming the helical arrangement.

5. Computer Modeling:

* Modern computer programs can simulate the behavior of molecules based on their chemical structure and interactions.

* Using experimental data and theoretical models, researchers can build and analyze virtual models of DNA, further validating the helical structure.

While each technique contributes to our understanding of the DNA helix, X-ray diffraction played a crucial role in the initial discovery and remains a cornerstone of structural biology.