Question

Write down the salient features of double helix structure of DNA.

Answer 1

1. Two polynucleotide strands: DNA consists of two long chains of nucleotides running alongside each other.
2. Antiparallel orientation: the two strands run in opposite directions (one 5’ → 3’, the other 3’ → 5’).
3. Right‑handed double helix (B‑form): the common form is a right‑handed helix.
4. Complementary base pairing: bases pair specifically adenine (A) with thymine (T) and guanine (G) with cytosine (C) via hydrogen bonds (A – T = 2 H‑bonds; G – C = 3 H‑bonds).