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: Understanding DNA conformation.
In aqueous solution, DNA most commonly exists in the B-form. This is the most stable structure under physiological conditions.
Step 2: Base pairs per turn in B-DNA.
B-DNA has a right-handed helix with about 10.5 base pairs per helical turn. This allows optimal hydrogen bonding and spacing of base pairs.
Step 3: Other conformations.
- A-DNA: ~11 base pairs per turn, seen in dehydrated conditions.
- Z-DNA: Left-handed helix, ~12 base pairs per turn.
The physiological stable form remains B-DNA with 10.5 base pairs per turn.
Step 4: Conclusion.
Thus, the correct stable conformation is 10.5 base pairs per turn.
Final Answer: \[ \boxed{\text{The correct answer is (A) 10.5 base pair/turn.}} \]