Question

DNA conformation is left handed in

• A. DNA B
• B. DNA C
• C. DNA Z
• D. DNA A

Hint:

Z-DNA is the only naturally occurring left-handed DNA conformation. Remember: Z = Zig-zag = Left-handed.

Answer 1

The Correct Option is C

Step 1: Know the DNA conformations.
DNA can exist in multiple conformations. The major ones include:

• A-DNA: Right-handed helix, dehydrated form
• B-DNA: Right-handed helix, most common form in cells
• Z-DNA: Left-handed helix, forms in regions with alternating purine and pyrimidine sequences
• C-DNA: Also right-handed, observed under certain lab conditions

Step 2: Analyze the helical direction.
Right-handed helices: A-DNA, B-DNA, C-DNA
Left-handed helix: Z-DNA

Step 3: Z-DNA properties.
Z-DNA has a zig-zag phosphate backbone.
Forms under high salt concentrations or supercoiling.
Found transiently in regions of DNA under active transcription.

Step 4: Conclusion.
Only DNA Z is left-handed among the listed options.