Question

Match List-I with List-II

List-I (Form of DNA) & List-II (Characteristic of DNA)
(A). A-DNA & (II). Short, broad and right-handed
(B). B-DNA & (III). Longer, thinner and right-handed
(C). Z-DNA & (IV). Anti conformation at Cytosine and syn at Guanine
(D). H-DNA & (I). Triplex DNA

Choose the correct answer from the options given below:

• A. (A)-(I), (B)-(II), (C)-(III), (D)-(IV)
• B. (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
• C. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
• D. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)

Hint:

A-DNA and B-DNA are right-handed helices, while Z-DNA is left-handed. H-DNA represents a non-canonical triple-stranded (triplex) helical structure.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
DNA can adopt different structural conformations depending on hydration levels, salt concentrations, nucleotide sequences, and supercoiling.

Step 2: Detailed Explanation:
Let us match the forms of DNA with their structural characteristics:
- (A) A-DNA $\rightarrow$ (II) Short, broad and right-handed: Formed under dehydrating conditions, it is wider and has a shorter helical pitch than B-DNA.
- (B) B-DNA $\rightarrow$ (III) Longer, thinner and right-handed: This is the standard, biologically dominant double-helix conformation under highly hydrated physiological conditions.
- (C) Z-DNA $\rightarrow$ (IV) Conformation of glycosyl bond is anti at Cytosine and syn at Guanine: A left-handed double helix where the glycosidic bond alternates between anti (for pyrimidines like Cytosine) and syn (for purines like Guanine), giving it a zigzag backbone.
- (D) H-DNA $\rightarrow$ (I) Triplex DNA: A triple-helical DNA structure that forms in mirror-repeat polypurine/polypyrithidine tracts.
This matches Option (C).

Step 3: Final Answer:
The correct option is (C).