Question

Total number of complete spirals occurring in a segment of DNA having 100 nucleotides will be ................

• A. 5
• B. 6
• C. 3
• D. 4

Hint:

Each complete turn of the DNA helix typically corresponds to about 20 nucleotides.

Answer 1

The Correct Option is A

Step 1: Understanding the structure of DNA.
DNA has two strands that coil around each other to form a double helix. The number of complete spirals (turns of the helix) in a given segment depends on the number of nucleotides. Each complete spiral in the DNA helix corresponds to about 10 base pairs (20 nucleotides).
Step 2: Analyzing the options.
(A) 5: Correct. For 100 nucleotides, there will be 5 complete turns, as each turn of the helix contains approximately 20 nucleotides.
(B) 6: Incorrect. 6 turns would require 120 nucleotides.
(C) 3: Incorrect. 3 turns would require 60 nucleotides.
(D) 4: Incorrect. 4 turns would require 80 nucleotides.
Step 3: Conclusion.
The correct answer is (A) 5, as 100 nucleotides correspond to 5 complete spirals.