How many nucleotides are there in 3 complete twists in the helix? A 15 B 20 C 10 D 30

To determine the number of nucleotides in 3 complete twists of a DNA helix, we can follow these steps:

1. Break Down the Problem

• Understand that a complete twist of a DNA helix, also known as a turn, consists of a specific number of base pairs (nucleotides).

2. Relevant Concepts

• In a typical DNA double helix, there are approximately 10.5 base pairs per complete turn.

3. Analysis and Detail

• If 1 complete turn = 10.5 base pairs, then for 3 complete turns: $\text{Total nucleotides} = 3 \times 10.5 = 31.5$

Since we can only have whole nucleotides, we round 31.5 to the nearest whole number, which is 32.

4. Verify and Summarize

• Each complete turn contains approximately 10.5 nucleotides, thus for 3 turns, we calculated 31.5 and rounded to 32. There may not be an exact integer within the available options.

Final Answer

Since 32 is not listed among the options, it appears there may be an error in the provided choices, since none match the calculation which suggests that 32 nucleotides would be present in 3 complete twists. The closest option is D, but that is not reflective of the accurate calculation.