Chargaff’s rule states that the amount of in DNA is always roughly equal to the amount of thymine, and that the amount of guanine in DNA is always roughly equal to the amount of cytosine.
The outside of the DNA double helix is made of alternating groups of deoxyribose sugars and .
The DNA double helix is , meaning that the two strands run in opposite directions.
Respond to the following based on your reading.

What's x-ray crystallography?
Explain how Rosalind Franklin's x-ray crystallography work helped Watson and Crick in their quest to determine the physical structure of DNA.
What did Watson, Crick, and Franklin discover about the structure of DNA?
How did Watson, Crick, and Franklin's work reiterate Chargaff's findings?