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Hermann Henking
Hermann Paul August Otto Henking (16 June 1858 – 28 April 1942) was a German cytologist who discovered the X chromosome in 1890 or 1891. The work was the result of a study in Leipzig of the testicles of the firebug (''Pyrrhocoris apterus''), during which Henking noticed that one chromosome did not take part in meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c .... 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 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 Chromos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 functioning of organisms. Cell biology is the study of the structural and functional units of cells. Cell biology encompasses both prokaryotic and eukaryotic cells and has many subtopics which may include the study of cell metabolism, cell communication, cell cycle, biochemistry, and cell composition. The study of cells is performed using several microscopy techniques, cell culture, and cell fractionation. These have allowed for and are currently being used for discoveries and research pertaining to how cells function, ultimately giving insight into understanding larger organisms. Knowing the components of cells and how cells work is fundamental to all biological sciences while also being essential for research in biomedical fields suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X Chromosome
The X chromosome is one of the two sex chromosomes in many organisms, including mammals, and is found in both males and females. It is a part of the XY sex-determination system and XO sex-determination system. The X chromosome was named for its unique properties by early researchers, which resulted in the naming of its counterpart Y chromosome, for the next letter in the alphabet, following its subsequent discovery. Discovery It was first noted that the X chromosome was special in 1890 by Hermann Henking in Leipzig. Henking was studying the testicles of '' Pyrrhocoris'' and noticed that one chromosome did not take part in meiosis. Chromosomes are so named because of their ability to take up staining (''chroma'' in Greek means ''color''). Although the X chromosome could be stained just as well as the others, Henking was unsure whether it was a different class of the object and consequently named it ''X element'', which later became X chromosome after it was established that it w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leipzig
Leipzig (, ; ; Upper Saxon: ; ) is the most populous city in the States of Germany, German state of Saxony. The city has a population of 628,718 inhabitants as of 2023. It is the List of cities in Germany by population, eighth-largest city in Germany and is part of the Central German Metropolitan Region. The name of the city is usually interpreted as a Slavic term meaning ''place of linden trees'', in line with many other Slavic placenames in the region. Leipzig is located about southwest of Berlin, in the southernmost part of the North German Plain (the Leipzig Bay), at the confluence of the White Elster and its tributaries Pleiße and Parthe. The Leipzig Riverside Forest, Europe's largest intra-city riparian forest, has developed along these rivers. Leipzig is at the centre of Neuseenland (''new lake district''). This district has Bodies of water in Leipzig, several artificial lakes created from former lignite Open-pit_mining, open-pit mines. Leipzig has been a trade city s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrrhocoris Apterus
The firebug, ''Pyrrhocoris apterus'', is a common insect of the family Pyrrhocoridae. Easily recognizable due to its striking red and black coloration, it may be confused with the similarly coloured though unrelated '' Corizus hyoscyami'' (cinnamon bug or squash bug). ''Pyrrhocoris apterus'' is distributed throughout the Palaearctic from the Atlantic coast of Europe to northwest China. It has also been reported from the United States, Central America, and India, and is also found in Australia. It has been reported as recently expanding its distribution northwards into mainland United Kingdom and eastward on to the coast of the Mediterranean Sea. They are frequently observed to form aggregations, especially as immature forms, containing from tens to perhaps a hundred individuals. Reproduction Firebugs generally mate in April and May. Their diet consists primarily of seeds from lime trees and mallows ( see below). They can often be found in groups near the base of lime tree t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiosis
Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome (haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the original parent cell. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, after a year of teaching he entered the college as a graduate student (A.B.,1896, A.M.,1898, and Ph.D.,1902.) He studied one summer with W.M. Wheeler at the University of Chicago and at his suggestion, studied the spermatogenesis of Xiphidium fasciatum, a long-horned grasshopper; launching his scientific career in the research of chromosomes. McClung took advantage of the great abundance of grasshoppers in Kansas ''"to make them pivotal for cytological study and to found a school of grasshopper cytologists''." Later, the use of Brachystola magna ("Lubber" grasshopper) for cytological studies would spread to laboratories throughout the world, as germ-cells in the testes were very large and easily studied. Development of the “McClung Mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex Determination System
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two common sexes, males and females, and in other species, there are hermaphrodites, organisms that can function reproductively as either female or male, or both. There are also some species in which only one sex is present, temporarily or permanently. This can be due to parthenogenesis, the act of a female reproducing without fertilization. In some plants or algae the gametophyte stage may reproduce itself, thus producing more individuals of the same sex as the parent. In some species, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology. In animals this is often accompanied by chromosomal differences, generally through combinations of XY, ZW, XO, ZO chromosomes, or haplodiploidy. The sexual dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1858 Births
Events January–March * January 9 ** Revolt of Rajab Ali: British forces finally defeat Rajab Ali Khan of Chittagong. ** Anson Jones, the last president of the Republic of Texas, commits suicide. * January 14 – Orsini affair: Piedmontese revolutionary Felice Orsini and his accomplices fail to assassinate Napoleon III in Paris, but their bombs kill eight and wound 142 people. Because of the involvement of French émigrés living in Britain, there is a brief anti-British feeling in France, but the emperor refuses to support it. * January 25 – The '' Wedding March'' by Felix Mendelssohn becomes a popular wedding recessional, after it is played on this day at the marriage of Queen Victoria's daughter Victoria, Princess Royal, to Prince Friedrich of Prussia in St James's Palace, London. * January ** Benito Juárez becomes the Liberal President of Mexico and its first indigenous president. At the same time, the conservatives installed Félix María Zuloaga as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1942 Deaths
The Uppsala Conflict Data Program project estimates this to be the deadliest year in human history in terms of conflict deaths, placing the death toll at 4.62 million. However, the Correlates of War estimates that the prior year, 1941, was the deadliest such year. Death toll estimates for both 1941 and 1942 range from 2.28 to 7.71 million each. Events Below, the events of World War II have the "WWII" prefix. January * January 1 – WWII: The Declaration by United Nations is signed by China, the United Kingdom, the United States, the Soviet Union, and 22 other nations, in which they agree "not to make any separate peace with the Axis powers". * January 5 – WWII: Two prisoners, British officer Airey Neave and Dutch officer Anthony Luteyn, escape from Colditz Castle in Germany. After travelling for three days, they reach the Swiss border. * January 7 – WWII: ** Battle of Slim River: Japanese forces of the 5th Division, supported by tanks, sweep through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
