Joe Hin Tjio (2 November 1919 – 27 November 2001), was an Indonesian-born American cytogeneticist. He was renowned as the first person to recognize the normal number of human
chromosome
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
s on December 22, 1955 at the Institute of Genetics of the
University of Lund
, motto = Ad utrumque
, mottoeng = Prepared for both
, established =
, type = Public research university
, budget = SEK 9 billion Sweden, where Tjio was a visiting scientist.
Early life
Tjio (whose name is pronounced ''CHEE-oh'') was born to Indonesian parents of Chinese origin in
Pekalongan
Pekalongan ( jv, ꦦꦼꦏꦭꦺꦴꦔꦤ꧀) is a city of Central Java, Indonesia. It was formerly the seat of Pekalongan Regency on the northern coast of the province, but is now an independent municipality within the province. The city is Cen ...
,
Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mos ...
, then part of the Dutch East Indies and later known as Indonesia. His father was a photographer. Tjio was educated in Dutch colonial schools, trained in agronomy in college, and did research on potato breeding. He was imprisoned for 3 years and tortured by the Japanese in a
concentration camp
Internment is the imprisonment of people, commonly in large groups, without charges or intent to file charges. The term is especially used for the confinement "of enemy citizens in wartime or of terrorism suspects". Thus, while it can simpl ...
during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
.
Career
After the war ended, Tjio went to the
Netherlands
)
, anthem = ( en, "William of Nassau")
, image_map =
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Kingdom of the Netherlands
, established_title = Before independence
, established_date = Spanish Netherl ...
, whose government provided him with a fellowship for study in Europe. He worked in plant breeding in
Denmark
)
, song = ( en, "King Christian stood by the lofty mast")
, song_type = National and royal anthem
, image_map = EU-Denmark.svg
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Kingdom of Denmark
, establish ...
,
Spain
, image_flag = Bandera de España.svg
, image_coat = Escudo de España (mazonado).svg
, national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond")
, national_anthem = (English: "Royal March")
, i ...
and Sweden. From 1948 to 1959 he did plant chromosome research in
Zaragoza
Zaragoza, also known in English as Saragossa,''Encyclopædia Britannica'"Zaragoza (conventional Saragossa)" is the capital city of the Zaragoza Province and of the autonomous community of Aragon, Spain. It lies by the Ebro river and its tributari ...
in Spain and spent his summers in Sweden working with Professor Albert Levan in Lund.
In 1955, Tjio made his discovery of the correct human chromosome count (46 chromosomes, rather than 48 as counted in 1921 by
Theophilus Painter
Theophilus Shickel Painter (August 22, 1889 – October 5, 1969) was an American zoologist best known for his work on the structure and function of chromosomes, especially the sex-determination genes X and Y in humans. He was the first to discove ...
) and the findings were published (with Levan as his co-author) in the Scandinavian journal '' Hereditas'' on January 26, 1956.
In 1958 Tjio went to the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
and in 1959 he joined the staff of the
National Institutes of Health
The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
in
Bethesda, Maryland
Bethesda () is an unincorporated, census-designated place in southern Montgomery County, Maryland. It is located just northwest of Washington, D.C. It takes its name from a local church, the Bethesda Meeting House (1820, rebuilt 1849), which in ...
. He received his Ph.D. in biophysics and cytogenetics from the
University of Colorado
The University of Colorado (CU) is a system of public universities in Colorado. It consists of four institutions: University of Colorado Boulder, University of Colorado Colorado Springs, University of Colorado Denver, and the University o ...
. He spent the balance of his career at the NIH in human chromosome research. He was named scientist emeritus in 1992, but maintained a laboratory for the next five years. In 1997, he retired to
Gaithersburg, Maryland
Gaithersburg ( ), officially the City of Gaithersburg, is a city in Montgomery County, Maryland, United States. At the time of the 2020 U.S. Census, Gaithersburg had a population of 69,657, making it the ninth-largest location in the state. Gai ...