Dr. Tjio (pronounced CHEE-o), born in Java, Indonesia to Chinese parents on November 27, 1919, was educated in Dutch colonial schools, which required that he learn French, German and English, in addition to Dutch, and trained in agronomy in college. He became deeply involved in potato breeding as he matured as a scientist, trying to create a hybrid resistant to a common disease. In 1942, Tjio was imprisoned by the Japanese Imperial Army, which occupied his country. For three years, until World War II ended, Tjio languished in a concentration camp, enduring torture (for daring to provide medical help to those worse off than him) and "horrible things" that are still obviously painful to recall. When the war ended, he boarded a Red Cross boat for displaced persons and shipped to Holland, whose government provided him with a fellowship for study in Europe. He stayed half a year at the Royal Danish Academy in Copenhagen, then journeyed to the University of Lund in Sweden, where he began an association with the Institute of Genetics headed by Dr. Albert Levan. His work by now had broadened to include mammalian tissues. Tjio's successful research garnered the attention of the government of Spain, which invited him to work on a plant improvement program there. From 1948 to 1959, he directed cytogenetic research in Zaragoza, taking summers and holidays off to work with Levan in Sweden. Dr. Tjio was fluent in English, French, German, Italian, Russian and Spanish.
Dr. Tjio discovered the correct number of chromosomes in human cells. His groundbreaking finding, published in the Scandinavian journal Hereditas on Jan. 26, 1956, created great international excitement. He could count quite clearly in human embryonic lung tissue that there were 46 chromosomes, not 48, as had been science's best estimate in the preceding half century. In 1956, at the first International Human Genetics Congress in Copenhagen, Tjio was approached by Indiana University professor and Nobel laureate Herman Muller, who persuaded Tjio to consider emigrating to the United States, where his expertise was highly sought, especially by Dr. T.T. Puck at the University of Colorado. Tjio arrived at the University of Colorado in 1957 and earned his Ph.D. in 1960. His doctoral theses deals with the chromosomes of men. In 1959, he joined NIH as a visiting scientist.
On December 6, 1962, Dr. Tjio accepted a trophy from President John F. Kennedy honoring him as an International Prize Award winner of the Joseph P. Kennedy, Jr. Foundation. The prize recognized Tijo's work on mental retardation. He also received honorary doctoral degrees from University of Claude Bernard, France in 1974 and Science University, Zaragosa, Spain in 1981.
At NIH, Tjio built on the ramifications of his chromosome work, studying leukemia and mental retardation. Ironically, his son suffered complications at birth and was affected by the latter condition. In February 1992 Tjio retired with the status of scientist emeritus. He died on November 27 at the Asbury Methodist Village in Gaithersburg, Maryland. He is survived by his wife, Inga, and one son. (Summary of the story by Dr. Gordon Allen).