Question

which of the following characteristics of the structure of dna was determined directly from x - ray diffraction photographs of crystallized dna?
the frequency of a versus t nucleotides
the sequence of nucleotides
the length of a given dna molecule
the double helical structure

Explanation:

X - ray diffraction is a technique that can reveal the overall three - dimensional structure of a molecule. The double helical structure of DNA was deduced from the X - ray diffraction photographs (like Rosalind Franklin's famous Photo 51). The frequency of A versus T nucleotides (Chargaff's rules) was determined by chemical analysis of nucleotide composition. The sequence of nucleotides is determined by sequencing techniques (not X - ray diffraction). The length of a given DNA molecule is not directly obtained from X - ray diffraction which is more about the repeating structural pattern.

Answer:

the double helical structure