---
id:"kb-2026-00336"
title:"DNA Structure"
schema_type:"TechArticle"
category:"science"
language:"en"
confidence:"high"
last_verified:"2026-05-22"
generation_method:"ai_assisted"
ai_models:["claude-opus"]
derived_from_human_seed:true
primary_sources:
  - title:"The Double Helix (James Watson, 1968)"
    type:"book"
    year:1968
    url:"https://www.simonandschuster.com/books/The-Double-Helix/James-D-Watson/9780743216302"
    institution:"Atheneum"
secondary_sources:
  - title: "MDN Web Docs — HTTP"
    type: "documentation"
    year: 2026
    url: "https://developer.mozilla.org/en-US/docs/Web/HTTP"
    institution: "Mozilla"
completeness: 0.88
ai_citations:
  last_citation_check:"2026-05-22"
---

## TL;DR

DNA (deoxyribonucleic acid) is the molecule carrying genetic instructions. Watson, Crick, and Wilkins (1953, Nobel 1962) - with crucial X-ray crystallography data from Rosalind Franklin - determined DNA's double helix structure: two antiparallel strands of sugar-phosphate backbone linked by complementary base pairs (A-T, G-C).

## Core Explanation

Nucleotides: Adenine (A), Thymine (T), Guanine (G), Cytosine (C). A pairs with T (2 hydrogen bonds), G pairs with C (3 bonds — stronger). DNA replication: helicase unwinds → DNA polymerase adds complementary bases → two identical copies. Human genome: ~3 billion base pairs, ~20,000-25,000 genes. Central dogma: DNA → RNA (transcription) → protein (translation).

## Further Reading

- [The Double Helix (James Watson, 1968)](https://www.simonandschuster.com/books/The-Double-Helix/James-D-Watson/9780743216302)