DNA (deoxyribonucleic acid) is the molecule that stores the hereditary information of almost all living organisms. The nucleus of a human cell holds about 3 billion base pairs, and more than 99% of them are the same in all people.
The information is coded by just four "letters" — the bases A, T, G and C. The order of these letters in the genes determines which proteins the cell makes. And which genes are switched on is largely regulated by epigenetics, in particular DNA methylation.
Structure of the double helix
DNA is two strands twisted into a double helix. Each "rung" of the ladder is formed by a pair of bases: adenine (A) always joins with thymine (T), and guanine (G) with cytosine (C). The side "rails" are made of alternating sugar (deoxyribose) and phosphate molecules. The combination "base + sugar + phosphate" is called a nucleotide — the elementary "building block" of DNA.
From gene to protein
A gene is a stretch of DNA with the instruction for one protein (or RNA). The cell reads the sequence of letters and from it assembles proteins — the working molecules of the body. Before division, DNA is copied in full so that each daughter cell gets an exact copy. Although the human genome is almost 99.9% the same in all people, the remaining differences are what define our individuality.
DNA, damage and aging
Over a lifetime DNA is constantly damaged — by ultraviolet light, free radicals, copying errors — and repair systems do not always manage to fix everything. The accumulation of such damage is considered one of the causes of aging. The ends of chromosomes are protected from "wear" by telomeres. A separate, reversible "setting" — DNA methylation — "drifts" with age; the epigenetic clocks that estimate biological age are based on this. Mitochondria also have their own separate DNA.
Calculate using this marker
Calculators where DNA is used directly:
Frequently asked questions
How does DNA differ from a gene?
DNA is the whole molecule that carries heredity. A gene is a specific stretch of it with the instruction for one protein. A single DNA molecule contains thousands of genes and many non-coding regions.
Can you change your DNA through lifestyle?
Lifestyle does not change the actual sequence of DNA letters. But it influences epigenetics — which genes are switched on — through DNA methylation and other marks on top of the genes.