What Is DNA
Last updated: March 31, 2026
Quick Answer: DNA (deoxyribonucleic acid) carries the genetic instructions for all living organisms. It's a double helix of two strands with four chemical bases: adenine (A), thymine (T), guanine (G), and cytosine (C). A always pairs with T, G always pairs with C.
Key Facts
- Human DNA has ~3 billion base pairs and 20,000-25,000 genes
- Uncoiled DNA from one cell stretches about 2 meters
- Humans share 99.9% DNA with each other and ~60% with bananas
- Structure discovered by Watson and Crick in 1953, with crucial work by Rosalind Franklin
- Only 1-2% of DNA codes for proteins
Structure
A twisted ladder: sugar-phosphate sides, base-pair rungs. A-T and G-C base pairing allows accurate copying.
How DNA Works
Genes are DNA segments coding for proteins:
- Transcription: Gene copied into mRNA in the nucleus
- Translation: Ribosomes read mRNA and assemble proteins
Central Dogma: DNA → RNA → Protein
DNA Replication
Before cell division, the helix unzips. Each strand templates a new complementary strand. DNA polymerases copy with ~1 error per billion base pairs.
Applications
- Forensics: DNA fingerprinting identifies individuals
- Medicine: Genetic testing, gene therapy
- Ancestry: Trace ethnic background
- Agriculture: GMO crops
Related Questions
How is DNA different from RNA?
DNA is double-stranded with thymine. RNA is single-stranded with uracil. DNA stores info long-term; RNA carries temporary copies for protein building.
Sources
- Wikipedia — DNA CC-BY-SA-4.0
- MedlinePlus — DNA public_domain