Final answer:
Rosalind Franklin used X-ray diffraction methods to study DNA molecules and discovered the double helix structure of DNA, which is crucial for understanding genetic information.
Step-by-step explanation:
Rosalind Franklin used X-ray diffraction methods to study DNA molecules. Her X-ray diffraction images of DNA provided crucial information that allowed James Watson and Francis Crick to confirm that DNA forms a double helix structure. This discovery of the helical nature of DNA was instrumental in understanding the storage and replication of genetic information.