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Q.
DNA double helix diameter measures
Molecular Basis of Inheritance
Solution:
In $1953$, Rosalind Franklin, a student of Maurice $H.F$. Wilkins analysed X-ray diffraction pictures of crystalline DNA and concluded that it is a long molecule consisting of two similar strands running in helical manner. The structure also showed regular stacks. The helix makes one complete spiral turn every $3.4 \,nm$ and has a diameter of $2 \,nm$ or $20 \,\mathring{A}$ The distance between adjacent stacks is $0.34\, nm$.