Question

A stable conformation for DNA in a solution is:

• A. 10.5 base pair/turn
• B. 9.5 base pair/turn
• C. 10.0 base pair/turn
• D. 8.0 base pair/turn

Hint:

Always remember: B-DNA is the most common and stable form under physiological conditions, with 10.5 bp/turn.

Answer 1

The Correct Option is A

Step 1: DNA Conformation.
DNA typically adopts the B-form in aqueous solution, representing its most stable structure under physiological conditions.
Step 2: B-DNA Base Pairs.
B-DNA is a right-handed helix, characterized by approximately 10.5 base pairs per helical turn, which facilitates optimal hydrogen bonding and base pair spacing.
Step 3: Alternative Conformations.
- A-DNA: Comprises roughly 11 base pairs per turn and is observed under dehydrated conditions.
- Z-DNA: Features a left-handed helix with approximately 12 base pairs per turn.
B-DNA remains the physiologically stable form at 10.5 base pairs per turn.
Step 4: Summary.
Therefore, the stable conformation is determined to be 10.5 base pairs per turn.
Final Answer: \[ \boxed{\text{The correct answer is (A) 10.5 base pair/turn.}} \]