What are the main structural features of DNA found in the Z conformation?

• A. Left-handed helix with a smooth sugar-phosphate backbone
• B. Right-handed helix with a smooth sugar-phosphate backbone
• C. Left-handed helix with a zigzag sugar-phosphate backbone
• D. Right-handed helix with a zigzag sugar-phosphate backbone

Answer: (C)

Verified step by step guidance

1. Understand that DNA can exist in different conformations, with the most common being the B-DNA form. However, Z-DNA is another form that is less common and has distinct structural features.
2. Recognize that Z-DNA is characterized by its left-handed helical structure, which is opposite to the right-handed helix of B-DNA.
3. Identify the sugar-phosphate backbone of Z-DNA, which is not smooth but has a zigzag pattern. This zigzag pattern is a key feature that differentiates Z-DNA from other DNA conformations.
4. Consider the environmental conditions that favor the formation of Z-DNA, such as high salt concentrations or the presence of certain sequences rich in guanine and cytosine.
5. Note that the structural features of Z-DNA, including the left-handed helix and zigzag backbone, can influence its biological functions and interactions with proteins.