What is DNA?
DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for living things. It is shaped like a twisted ladder called a double helix.
The rungs of the DNA ladder are made of four chemical bases: adenine, thymine, guanine and cytosine, usually written A, T, G and C. A always pairs with T, and G with C. The order of these bases along the molecule spells out genes, which tell cells how to make proteins.
Almost every cell in your body contains about 2 meters of DNA, tightly coiled into 46 chromosomes. The full set of human DNA, called the genome, has about 3 billion base pairs and around 20,000 protein-coding genes.
Who discovered its shape?
James Watson and Francis Crick described the double helix in 1953, using data from Rosalind Franklin and Maurice Wilkins, including Franklin's X-ray image called Photo 51. The Human Genome Project published the first nearly complete human genome sequence in 2003.
Did You Know?
About 99.9 percent of the DNA of any two people is identical. The tiny differences help make each person unique and are used in DNA testing.