Question

DNA double helix diameter measures

• A. $20\mu m$
• B. 20 mm
• C. $20\mathring{A}$
• D. 20 nm

Answer 1

Answer: (C)

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 $3.4nm$ and has a diameter of $2nm$ or $20\mathring{A}$ The distance between adjacent stacks is $0.34nm$.