Discovery
In 1869 Swiss physician Friedrich Miescher extracted a phosphorus-rich substance from the nuclei of white blood cells in pus-soaked bandages and called it "nuclein." For decades, though, scientists assumed genes were made of more complex proteins. In 1944 Oswald Avery, Colin MacLeod and Maclyn McCarty showed that the "transforming principle" that changed pneumococcal bacteria was DNA, and in 1950 Erwin Chargaff found that A matches T and G matches C in quantity. The physical basis of Mendel's hereditary factors was coming into view.
The double helix
In 1952 Rosalind Franklin and Raymond Gosling at King's College London captured "Photo 51," an X-ray diffraction image that clearly showed a helix. After seeing the data through Maurice Wilkins, James Watson and Francis Crick at Cambridge published their model in Nature in April 1953: two strands running in opposite directions, paired A–T and G–C. The three men shared the 1962 Nobel Prize; Franklin, who died in 1958 at 37, was not included, and her credit remains one of science's best-known controversies.
The genomic era
The double helix showed how each strand could serve as a template for copying, and the "central dogma" of DNA to RNA to protein followed. The Human Genome Project, launched in 1990, declared about 92% of the sequence done in 2003, and in 2022 the Telomere-to-Telomere consortium published the first truly complete human genome. DNA now underpins paternity and forensic testing, recombinant drugs like insulin, mRNA vaccines and precise edits with CRISPR.
FAQ
- How are DNA, genes and chromosomes different?
- DNA is the molecule; a gene is a stretch of DNA that encodes a protein or other product; a chromosome is DNA wound around proteins into a compact package. Humans have 23 pairs.
- How similar is DNA between people?
- Any two people share about 99.9% of their DNA sequence; the remaining 0.1% accounts for individual differences.
Sources reviewed: 2026-10-26
References
- Watson, J. D., & Crick, F. H. C. (1953). Molecular structure of nucleic acids: a structure for deoxyribose nucleic acid. Nature, 171, 737–738.
- Avery, O. T., MacLeod, C. M., & McCarty, M. (1944). Studies on the chemical nature of the substance inducing transformation of pneumococcal types. Journal of Experimental Medicine, 79(2), 137–158.
- Nurk, S., et al. (2022). The complete sequence of a human genome. Science, 376(6588), 44–53.