How did Chargaff's first rule support Watson and Crick's model for the structure of DNA?

Question

anonymous · Answer

Chargaff's rule says the quantities of the nucleotide pairs match or the rule can be stated that there is a 1:1 ratio in paired pyrimidine and purine bases. 
A adenine = T thymidine 
G guanine = C cytosine

anonymous · Answer

C & W used a stick and ball system to model the helical structure. The x-ray crystalographic picture Rosalyn Franklin took gave them the the information that structure coiled in a double helix. Further Franklin gave them what the slope and spacing of the coils and its units assumed and that the phosphate backbone was on the outside. This meant the Chargaff pairs fit inside the coil and the hydrogen pairs acted to anchor the two strands together.