Photography by benjamin saur tübingen walther

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Photography by Benjamin Saur, Tübingen.
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Walther Flemming, a German physician and physiologist investigating the structure of cells, discovered a nuclear substance he called “ chromatin” because it was intensely stained with aniline dyes. He noticed that, during cell division, this substance separates into threadlike strings , which were later named chromosomes” (by Heinrich Waldemeyer). 1882 - Walther Flemming: Discovers chromatin & mitotic division of chromosomes The new staining techniques made it possible for Flemming to follow in far greater detail the process of cell division, which he named “ mitosis ” from the Greek for thread. Most importantly, Flemming detailed the fundamental process of mitosis, that is, the splitting of the chromosomes along their lengths into two identical halves. These results were published in the seminal book Zellsubstanz, Kern und Zelltheilung (1882; Cytoplasm, Nucleus and Cell Division). It was another 20 years before the significance of Flemming's work was truly realized with the rediscovery of Gregor Mendel's rules of heredity. "Further study of the division phenomena requires a brief discussion of the material which thus far I have called the stainable substance of the nucleus. Since the term nuclear substance could easily result in misinterpretation..., I shall coin the term chromatin for the time being. This does not indicate that this substance must be a chemical compound of a definite composition, remaining the same in all nuclei. Although this may be the case, we simply do not know enough about the nuclear substances to make such an assumption. Walther Flemming
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1900 - Carl Correns, Hugo de Vries, and Erich von Tschermak: independently rediscover Mendel's Laws. 1902 - Theodor Boveri and Walter Sutton: propose that the heredity units (called “genes”as of 1909) are located on chromosomes. Theodor Boveri (1862-1915 ), a German scientist , had previously shown that chromosomes remain organized through the process of cell division (MITOSIS), and he demonstrated that sperm and egg cells each contribute the same number of chromosomes . Boveri recognized the Mendelian concepts of segregation and assortment could be interpreted to operate on a cellular level, with chromosomes containing the "factors"—as Mendel called the genes. The probability was "extraordinarily high," wrote Boveri in 1903, "that the characters dealt with in Mendelian experiments are truly connected to specific chromosomes." Walter Sutton (1877-1916) , an American graduate student, came to the same conclusion at about the same time. Sutton, working with marine life forms, had also become familiar with the process of "reduction division" (later called MEIOSIS) , which gives rise to reproductive germ cells, or gametes. In meiosis, the number of chromosomes is reduced by half in sperm and egg cells, with the original number restored in the zygote, or fertilized egg, during reproduction. This process was consonant with Mendel's idea of segregation. In 1902 Sutton suggested that "the
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