Final answer:
Erwin Chargaff discovered that in DNA, the concentration of adenine equals that of thymine, and guanine equals cytosine, a set of regularities known as Chargaff's rules. These findings were fundamental in aiding Watson and Crick to determine the double helix structure of DNA, solidifying the base pairing mechanism crucial for DNA replication.
Step-by-step explanation:
Erwin Chargaff, an Austrian-American biochemist, made crucial contributions to the discovery of the DNA molecule's structure through his research in the 1950s. Chargaff was fascinated by the four nitrogen bases of DNA - adenine (A), guanine (G), cytosine (C), and thymine (T). Through his experiments, he analyzed the base composition of DNA from various species and discovered key patterns which are known as Chargaff's rules.
Chargaff found that the concentrations of adenine and thymine were about equal, as were the concentrations of guanine and cytosine. This equated to A = T and G = C. His rules also pointed out that the ratios of A+T to G+C vary between species but are constant within a species. Chargaff's findings provided foundational knowledge that later helped James Watson and Francis Crick in formulating the double helix model of DNA. Specifically, his rules suggested that the nitrogen bases paired with each other, which was a crucial insight for understanding the DNA structure and its replication process.
Chargaff's rules have therefore been instrumental in furthering our understanding of DNA, particularly its secondary structure and the process of DNA replication, which is now known to occur in a semi-conservative manner during the cell cycle's synthesis phase. His contributions laid the groundwork for the transformative discovery of the double helix structure of DNA by Watson and Crick.