Question

rosalind franklins photographs of the x - ray diffraction pattern of dna provided important clues about the structure of the dna molecule. what was revealed by the photograph that enabled watson and crick to build their model of the dna molecule? select all that apply
a. the nitrogenous bases form the backbone on the outside of each dna strand.
b. the dna strands are twisted around each other.
c. there are two strands in the dna molecule.
d. the nitrogenous bases are near the center of the dna molecule.

Explanation:

Rosalind Franklin's X-ray diffraction image (Photo 51) of DNA revealed key structural features:

• The cross-shaped pattern indicated the DNA molecule is a double helix, meaning strands are twisted around each other (Option B).
• The symmetry and spacing in the diffraction pattern showed there are two strands in the molecule (Option C).
• The pattern also implied the nitrogenous bases are positioned near the center, with the sugar-phosphate backbone on the outside, ruling out Option A and confirming Option D.

Answer:

B. The DNA strands are twisted around each other.
C. There are two strands in the DNA molecule.
D. The nitrogenous bases are near the center of the DNA molecule.