Question

which statement best describes how watson and crick’s model used other scientists’ work to create a model of dna?

○ they used chargaff’s rule to determine that it contains ribose sugar.
○ they used franklin’s photo to determine that dna was a double helix.
○ they used levene’s work to determine the number of base pairs in each strand.
○ they used nirenberg and matthei’s studies to determine that dna is made of nucleotides.

Explanation:

• Option 1: DNA has deoxyribose, not ribose, and Chargaff's rule is about base pairing, so this is wrong.
• Option 2: Rosalind Franklin's X - ray diffraction photo (Photo 51) provided key evidence that helped Watson and Crick conclude DNA is a double helix, so this is correct.
• Option 3: Levene's work was on nucleotide structure, not base - pair number in strands, so this is wrong.
• Option 4: Nirenberg and Matthei's work was on genetic code (with RNA), not on DNA being made of nucleotides, so this is wrong.

Answer:

B. They used Franklin’s photo to determine that DNA was a double helix.