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It is named after John Langdon Down, the British doctor who fully described the syndrome in 1866. Some aspects of the condition were described earlier by Jean-Ãtienne Dominique Esquirol in 1838 and Ãdouard SÃ©guin in 1844. In 1957, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered.
Sir Joseph John Thomson, a British physicist, discovered the electron in 1897. In experiments studying electric discharge in cathode tubes, he noted a high value for the ratio of charge to mass. His...