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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. 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 Chromosom ... [...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 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 such as ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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-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 object and consequently named it ''X element'', which later be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 well as the second most populous city in the area of the former East Germany after (East) Berlin. Together with Halle (Saale), the city forms the polycentric Leipzig-Halle Conurbation. Between the two cities (in Schkeuditz) lies Leipzig/Halle Airport. Leipzig is located about southwest of Berlin, in the southernmost part of the North German Plain (known as Leipzig Bay), at the confluence of the White Elster River (progression: ) and two of its tributaries: the Pleiße and the Parthe. The name of the city and those of many of its boroughs are of Slavic origin. Leipzig has been a trade city since at least the time of the Holy Roman Empire. The city sits at the intersection of the Via Regia and the Via Imperii, two important medieval trad ... [...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 tru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 result in four cells 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 female will fuse to create a cell with two copies of each chromosome again, the zygote. 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 chr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clarence Erwin McClung
Clarence Erwin McClung (April 5, 1870 – January 17, 1946) was an eminent United States, American zoologist and prairie pioneer cytologist who discovered the role of chromosomes in Sex-determination system, 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 Ziphidium 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 studi ... [...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 sexes. In some species there are hermaphrodites. There are also some species that are only one sex due to parthenogenesis, the act of a female reproducing without fertilization. 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 differentiation is generally triggered by a main gene (a "sex locus"), with a multitude of other genes following in a domino effect. In other cases, sex of a fetus is determined by environmental variables (such as temperature). The details of some sex-determination systems are not yet fully understo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1858 Births
Events January–March * January – **Benito Juárez (1806–1872) becomes Liberal President of Mexico. At the same time, conservatives install Félix María Zuloaga (1813–1898) as president. **William I of Prussia becomes regent for his brother, Frederick William IV, who had suffered a stroke. * January 9 ** 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: 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 Pri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1942 Deaths
Year 194 ( CXCIV) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Septimius and Septimius (or, less frequently, year 947 ''Ab urbe condita''). The denomination 194 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. Events By place Roman Empire * Emperor Septimius Severus and Decimus Clodius Septimius Albinus Caesar become Roman Consuls. * Battle of Issus: Septimius Severus marches with his army (12 legions) to Cilicia, and defeats Pescennius Niger, Roman governor of Syria. Pescennius retreats to Antioch, and is executed by Severus' troops. * Septimius Severus besieges Byzantium (194–196); the city walls suffer extensive damage. Asia * Battle of Yan Province: Warlords Cao Cao and Lü Bu fight for control over Yan Province; the battle lasts for over 100 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
