Final answer:
The structure of DNA was discovered in the 1950s by James Watson and Francis Crick. Their research built upon the work of other scientists such as Erwin Chargaff and Rosalind Franklin. The correct answer to the student's question is the 1950s.
Step-by-step explanation:
The discovery of the structure of DNA occurred in the 1950s. It was during this era that James Watson and Francis Crick worked at the University of Cambridge to uncover the double-helix structure of DNA. They published their groundbreaking findings in 1953. This monumental discovery was built upon the work of other scientists such as Erwin Chargaff, who formulated Chargaff's rules, and Rosalind Franklin, whose expertise in X-ray diffraction was pivotal in revealing the structure of DNA. Chargaff's rules emphasized that the concentration of adenine (A) always equals the concentration of thymine (T) and the concentration of guanine (G) is always the same as that of cytosine (C). These findings set the stage for Watson and Crick's discovery. The understanding of DNA has profoundly impacted biology, medicine, and numerous other fields, allowing advancements in genetic engineering and biotechnology following the characterization of DNA's molecular structure.