Question

Which of the following is not relevant to the structure of double helical DNA?

• A. The helix makes one complete spiral turn every 34$\stackrel{\circ }{A}$
• B. The diameter of the helix is 20 $\stackrel{\circ }{A}$
• C. Each strand of helix has a backbone made up of alternating ribose sugar and phosphate
• D. The two adjacent sugar molecules are joined with phosphate by phosphodiester bond
• E. The distance between adjacent nucleotide is 3.4$\stackrel{\circ }{A}$

Answer 1

The correct option is C

Each strand of helix has a backbone made up of alternating ribose sugar and phosphate

The Watson and Crick model show that DNA is a double helix with deoxyribose and not ribose sugar. A covalent bond is formed between the 5' phosphate group of one nucleotide and the 3'-OH group of another -phosphate backbone on the outside and paired bases on the inside.