Answer:
For your first paragraph: While James Watson and Francis Crick are credited with discovering the structure of DNA, they would not have been able to do it on their own. Without photo 51, taken by Rosalind Franklin using X-ray chromatography, they would not have known that the shape was a double helix. Chargaff discovered that in DNA the number of guanine units is equal to the number of cytosine units, and the number of adenine units is equal to the number of thymine units. This hinted at the base pair makeup of DNA.
Step-by-step explanation:
For your first paragraph talk about the first prompt (What were the key contributions of the scientists involved in the discovery of the structure?). Watson and Crick were given the Nobel prize for there discovery of DNA's structure but Rosalind Franklin got a picture that proved the double helix, and Chargaff discovered that adenine went to thymine, and guanine went to cytosine.