---
id: kb-2026-00336
title: DNA Structure
schema_type: TechArticle
category: science
language: en
confidence: medium
last_verified: '2026-05-28'
created_date: '2026-05-22'
generation_method: ai_structured
ai_models:
  - claude-opus
derived_from_human_seed: true
conflict_of_interest: none_declared
is_live_document: false
data_period: static
atomic_facts:
  - id: fact-science-001
    statement: Watson and Crick's 1953 Nature paper proposed a double-helical structure for deoxyribose nucleic acid.
    source_title: 'Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid'
    source_url: https://doi.org/10.1038/171737a0
    confidence: medium
  - id: fact-science-002
    statement: NHGRI describes DNA sequencing as determining the order of the four bases adenine, cytosine, guanine, and thymine in a DNA molecule.
    source_title: DNA Sequencing Fact Sheet
    source_url: https://www.genome.gov/about-genomics/fact-sheets/DNA-Sequencing-Fact-Sheet
    confidence: medium
  - id: fact-science-003
    statement: Britannica describes the human genome as approximately three billion DNA base pairs and says coding regions encode roughly 20,000 to 25,000 genes.
    source_title: Human Genome
    source_url: https://www.britannica.com/science/human-genome
    confidence: medium
primary_sources:
  - title: 'Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid'
    type: academic_paper
    year: 1953
    authors:
      - Watson, James D.
      - Crick, Francis H. C.
    institution: Nature
    url: https://doi.org/10.1038/171737a0
    doi: 10.1038/171737a0
  - title: DNA Sequencing Fact Sheet
    type: government_report
    year: 2023
    institution: National Human Genome Research Institute
    url: https://www.genome.gov/about-genomics/fact-sheets/DNA-Sequencing-Fact-Sheet
  - title: Human Genome
    type: reference
    year: 2026
    institution: Encyclopaedia Britannica
    url: https://www.britannica.com/science/human-genome
completeness: 0.84
known_gaps:
  - This article focuses on DNA structure and genome-scale facts; the history of Rosalind Franklin's data and later molecular-biology developments need separate treatment.
---

## TL;DR

DNA is the hereditary molecule whose double-helical structure was proposed in 1953. Human genome summaries commonly describe roughly three billion base pairs and about 20,000 to 25,000 protein-coding genes.

## Core Explanation

This entry now avoids using memoir or generic textbook pages as evidence for precise genomic facts. The exported claims are mapped to the original Nature structure paper, NHGRI sequencing material, and Britannica's human-genome reference.

## Further Reading

- [Molecular Structure of Nucleic Acids](https://doi.org/10.1038/171737a0)
- [DNA Sequencing Fact Sheet](https://www.genome.gov/about-genomics/fact-sheets/DNA-Sequencing-Fact-Sheet)
- [Human Genome](https://www.britannica.com/science/human-genome)

## Related Articles

- [Genetics and Heredity](../genetics-and-heredity.md)
- [Molecular Biology Central Dogma](../molecular-biology-central-dogma.md)
- [Human Genome Project: Sequencing, Findings, and the Post-Genomic Era](../human-genome-project-sequencing-findings-and-the-post-genomic-era.md)