Hermann Paul August Otto Henking (16 June 1858 – 28 April 1942) was a German

cytologist Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and ...

who discovered the

X chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...

in 1890 or 1891. The work was the result of a study in

Leipzig Leipzig ( , ; Upper Saxon: ) is the most populous city in the German state of Saxony. Leipzig's population of 605,407 inhabitants (1.1 million in the larger urban zone) as of 2021 places the city as Germany's eighth most populous, as wel ...

of the testicles of the firebug (''Pyrrhocoris apterus''), during which Henking noticed that one chromosome did not take part in

meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...

. He named this the ''X element'' because its strange behaviour made him unsure whether it was genuinely a chromosome. It was later named the X chromosome after American cytologist

Clarence Erwin McClung Clarence Erwin McClung (April 5, 1870 – January 17, 1946) was an eminent American zoologist and prairie pioneer cytologist who discovered the role of chromosomes in sex-determination. Graduating pharmacy at the University of Kansas in 1892, ...

established that it was not only a genuine chromosome but a sex-determining one, though McClung incorrectly guessed that it was the male-determining sex chromosome.David Bainbridge, ''The X in Sex: How the X Chromosome Controls Our Lives'', pages 3–5, Harvard University Press, 2003 .

References

1858 births 1942 deaths 20th-century German biologists 19th-century German biologists {{Germany-biologist-stub