Question

Given figure represents the DNA double helix model as proposed by Watson and Crick $(1953)$. Select the option that shows correct measurements of $A, B$ and $C$.

• A. $A - 3.4\, nm, B - 0.34\, nm, C - 2 \,nm $
• B. $A-34 \,nm, B - 3.4\, nm, C - 20 \,nm$
• C. $A-3.4 \,\mathring{A}, B-0.34\,\mathring{A}, C-20\,\mathring{A} $
• D. $A - 34\, \mathring{A}, B - 3.4 \,\mathring{A}, C-2\,\mathring{A}$

Answer 1

Answer: (A)

The $DNA$ helix makes one complete spiral turn every $3.4 \,nm$ and has a diameter of $2\, nm$. The distance between adjacent stacks is $0.34\, nm$.