Final answer:
Watson and Crick's model of the DNA double helix built on Chargaff's rules for base pairing and Rosalind Franklin's X-ray diffraction evidence, leading to the discovery of DNA's structure and the crucial base pairing information that is essential for its function in genetic inheritance.
Step-by-step explanation:
James Watson and Francis Crick's model of DNA was extensively based on the work of other scientists, particularly through the utilization of Rosalind Franklin's X-ray diffraction photographs, which suggested the double helix shape, and Chargaff's rules that analyzed the pairing of DNA bases. Watson and Crick's groundbreaking work demonstrated that DNA is composed of two nucleotide strands wound around each other in a double helix, with sugars and phosphates on the outside, and the nucleotide bases adenine, thymine, guanine, and cytosine paired in a specific manner on the inside. The double helix structure is stabilized by hydrogen bonds between the complementary bases, a discovery that enabled the understanding of DNA replication and genetic inheritance.
Role of Chargaff’s Rules
Their model used Chargaff's rules to establish the base pairing. Chargaff found that DNA always contained equal amounts of adenine (A) and thymine (T), and guanine (G) and cytosine (C), which led to the understanding that A pairs with T and G with C. This was crucial for Watson and Crick’s model of the DNA double helix, as it explained the base pairing that held the two DNA strands together.
Use of Rosalind Franklin's X-ray Diffraction Photographs
Moreover, the duo used Rosalind Franklin's X-ray diffraction studies to confirm the helical structure of DNA. Franklin’s photo, often referred to as Photo 51, provided key insights into the dimensions of the DNA strands and the density of the nucleotides, factors that were critical for determining the shape of the DNA molecule.