The 30 Year Chromosome Mistake

In 1923, researcher Theophilus Painter became the first person to publish a human chromosome count after examining cells under a microscope, and he reported 24 pairs, or 48 total. Other scientists repeated his methods and copied the result, so the incorrect number stayed in textbooks and papers for more than 30 years. In 1956, cytogeneticist Joe Hin Tjio finally corrected the count to 46, ending the long-running error that had shaped human genetics research for decades.

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