59. The following feature about A-DNA is INCORRECT
1. The DNA is arranged in a left handed double helix
2. The base pairs in A-DNA are not perfectly perpendicular to the helix axis
3. The DNA is arranged in a right handed double helix
4. Number of base pairs per helical turn is 11

Answer: 1. The DNA is arranged in a left-handed double helix

Explanation:

A-DNA is one of the possible double-helix structures of DNA, typically observed under conditions of low humidity or in the presence of certain ions. Here’s an overview of the key features:

• Feature 1 (Incorrect): A-DNA is right-handed and not left-handed. This means the helix twists in a clockwise direction.

• Feature 2 (Correct): In A-DNA, the base pairs are indeed not perfectly perpendicular to the helix axis. They are tilted in the helical structure.

• Feature 3 (Correct): A-DNA is a right-handed helix, as stated above.

• Feature 4 (Correct): A-DNA has about 11 base pairs per helical turn. This is a characteristic feature of the A-DNA structure.

Conclusion:

The statement that A-DNA is arranged in a left-handed double helix (Feature 1) is incorrect. A-DNA has a right-handed helical structure. Therefore, Option 1 is the correct answer.