From Mendel's "factors" to genes
In 1866 Gregor Mendel, a friar in Brünn (now Brno, Czech Republic), reported crosses of roughly 28,000 pea plants showing that traits do not blend but pass on as paired "factors" following laws of dominance and segregation. The paper was largely ignored for 34 years until Hugo de Vries, Carl Correns and Erich von Tschermak independently rediscovered it in 1900. In 1909 the Danish botanist Wilhelm Johannsen named the factor a "gene", and in 1910 Thomas Hunt Morgan used a white-eyed fruit-fly mutant to show that genes sit on chromosomes. Darwin's natural selection and Mendelian genetics were united in the "modern synthesis" of the 1930s and 1940s.
What genes are and how they work
In 1941 George Beadle and Edward Tatum proposed that one gene makes one enzyme, and in 1944 Oswald Avery presented evidence that hereditary material is DNA rather than protein. When James Watson and Francis Crick revealed the double helix in 1953, it became clear that genetic information is stored and copied as the order of four bases, A, T, G and C. Genes are transcribed into RNA, and RNA is translated into protein. In 1961 François Jacob and Jacques Monod's operon model showed that bacteria switch genes on and off only when needed, revealing gene regulation. Cells with identical genes become brain or skin cells depending on which genes they switch on. Some traits, such as ABO blood type, depend on a single gene, but most — height, intelligence, disease risk — reflect many genes acting together with the environment.
Reading and editing the genome
In The Selfish Gene (1976) Richard Dawkins popularised a gene's-eye view of evolution — a metaphor, not a claim that genes have selfish minds. In 2001 the Human Genome Project published a draft of the roughly 3 billion base pairs, revealing far fewer protein-coding genes than expected, about 20,000, covering little more than 2% of the genome. In 2012 Jennifer Doudna and Emmanuelle Charpentier turned the system bacteria use to fight viruses into CRISPR-Cas9, a tool for cutting DNA at chosen sites, winning the 2020 Nobel Prize in Chemistry; in 2023 the first CRISPR-based therapy, for sickle-cell disease, was approved. The 2018 birth of gene-edited babies in China drew international condemnation and made the ethics of editing heritable DNA a major issue. Genetic test results describe probabilities, so interpret them with a genetic counsellor or doctor.
FAQ
- Are genes and DNA the same thing?
- DNA is the whole molecule carrying genetic information; a gene is a particular stretch of it with the instructions for a protein or RNA. If DNA is the book, genes are its sentences or paragraphs.
- Are personality and intelligence set by genes?
- Twin studies show genes clearly matter, but the effect comes from thousands of genes with tiny effects plus environment and experience. No single "intelligence gene" decides it.
Sources reviewed: 2026-10-26
References
- Mendel, G. (1866). Versuche über Pflanzen-Hybriden. Verhandlungen des naturforschenden Vereines in Brünn, 4, 3–47.
- Johannsen, W. (1909). Elemente der exakten Erblichkeitslehre. Jena: Gustav Fischer.
- Morgan, T. H. (1910). Sex limited inheritance in Drosophila. Science, 32(812), 120–122.
- Beadle, G. W., & Tatum, E. L. (1941). Genetic control of biochemical reactions in Neurospora. PNAS, 27(11), 499–506.
- 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.
- Watson, J. D., & Crick, F. H. C. (1953). Molecular structure of nucleic acids: A structure for deoxyribose nucleic acid. Nature, 171(4356), 737–738.
- Jacob, F., & Monod, J. (1961). Genetic regulatory mechanisms in the synthesis of proteins. Journal of Molecular Biology, 3(3), 318–356.
- Dawkins, R. (1976). The Selfish Gene. Oxford: Oxford University Press.
- Lander, E. S., et al. (International Human Genome Sequencing Consortium). (2001). Initial sequencing and analysis of the human genome. Nature, 409(6822), 860–921.
- Jinek, M., et al. (2012). A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science, 337(6096), 816–821.