The idea of the Weismann barrier is central to the modern evolutionary synthesis, though it is not expressed today in the same terms. In Weismann's opinion the random process of mutation in the gametes (or stem cells which make them) is the only source of change for natural selection to work on. Weismann was one of the first biologists to deny the inheritance of acquired characters entirely. Weismann's ideas came before the rediscovery of Gregor Mendel's work. Though Weismann was cagey about accepting Mendelism, younger workers soon made the connection.
Weismann's demarkation between germ-line and soma rested on the work of (mostly) German biologists during the second half of the 19th century. This was the time that the mechanisms of cell division began to be understood. Eduard Strasburger, Walther Flemming, and the Belgian Edouard Van Beneden laid the basis for the cytology and cytogenetics of the 20th century. Strasburger, the outstanding botanical physiologist of that century, coined the terms nucleus and cytoplasm. He said "new cell nuclei can only arise from the division of other cell nuclei". Van Beneden discovered how chromosomes combined at meiosis, during the production of gametes. Walther Flemming, the founder of cytogenetics, named mitosis, and pronounced "omne nucleus e nuclei" (which means the same as Strasburger's dictum). The discovery of mitosis, meiosis and chromosomes is regarded as one of the 100 most important scientific discoveries of all times, and one of the 10 most important discoveries in cell biology.
Meiosis was discovered and described for the first time in sea urchin eggs in 1876, by Oscar Hertwig. It was described again in 1883, at the level of chromosomes, by Van Beneden in "Ascaris" eggs. The "significance of meiosis for reproduction and inheritance", however, was first described in 1890 by Weismann, who noted that two cell divisions were necessary to transform one diploid cell into four haploid cells if the number of chromosomes had to be maintained. Thus the work of the earlier cytologists laid the ground for Weismann, who turned his mind to the consequences for evolution, which was an aspect the cytologists had not addressed. All this took place before the work of Mendel had been rediscovered
Theodor Boveri
Theodor Heinrich Boveri (12 October 1862 – 15 October 1915) was a German biologist who made discoveries in cytology, embryology and genetics. His career was devoted to the processes whereby a new individual arises from parental reproductive materials.
His work with sea urchins showed that it was necessary to have all chromosomes present in order for proper development of the embryo to take place. This discovery was an important part of the Boveri-Sutton chromosome theory. His other significant discovery was the centrosome (1888), which he described as the "especial organ of cell division". Boveri also discovered the phenomenon of chromatin diminution during embryonic development of the nematode "Parascaris".
1902–1904: Boveri, in a series of papers, drew attention to the correspondence between the behaviour of chromosomes and the results obtained by Mendel. He said that chromosomes were "independent entities which retain their independence even in the resting nucleus... What comes out of the nucleus is what goes into it".
In 1903 Walter Sutton suggested that chromosomes, which segregate in a Mendelian fashion, are hereditary units. E.B. Wilson, who was Sutton's teacher, called this the "Sutton–Boveri hypothesis".
Boveri reasoned that a cancerous tumor begins with a single cell in which the make up of its chromosomes becomes scrambled, causing the cells to divide uncontrollably.
It was only later that researchers such as Thomas Hunt Morgan showed that Boveri was correct.
Fred Hoyle
Sir Fred Hoyle (24 June 1915 – 20 August 2001) was an English astronomer. He is noted mainly for being the first man to think of the idea that nuclear fusion might happen in stars, like our Sun. In addition to his work as an astronomer, Hoyle was a writer of science fiction, including a number of books co-written with his son Geoffrey Hoyle. Fred Hoyle gave the Big Bang theory its name in a radio broadcast.
Awards
Edmund Beecher Wilson
Edmund Beecher Wilson (Geneva, Illinois, 19 October 1856 – 3 March 1939) was a pioneering American zoologist and cell biologist. He wrote one of the most famous textbooks in the history of modern biology, "The Cell".
Wilson graduated from Yale in 1878. He earned his doctorate at Johns Hopkins in 1881. He was a lecturer at Williams College in 1883–84 and at the Massachusetts Institute of Technology in 1884–85. He served as professor of biology at Bryn Mawr College from 1885 to 1891.
He spent the balance of his career at Columbia University where he was successively adjunct professor of biology (1891–94), professor of invertebrate zoology (1894–1897), and professor of zoology (from 1897).
Wilson is credited as America's first cell biologist. In 1898 he used the similarity in embryos to describe evolutionary relationships. By observing spiral cleavage in molluscs, flatworms and annelids he concluded that the same organs came from the same group of cells and concluded that all these organisms must have a common ancestor.
He also discovered the chromosomal XY sex-determination system in 1905—that males have XY and females XX sex chromosomes. Nettie Stevens independently made the same discovery the same year.
In 1907, he described, for the first time, the additional or supernumerary chromosomes, now called B-chromosomes.
Professor Wilson published many papers on embryology, and served as President of the American Association for the Advancement of Science in 1913.
The American Society for Cell Biology annually awards the E.B. Wilson Medal in his honour.
1902–1904: Theodor Boveri (1862–1915), a German biologist, in a series of papers, drew attention to the correspondence between the behaviour of chromosomes and the results obtained by Mendel. He said that chromosomes were "independent entities which retain their independence even in the resting nucleus... What comes out of the nucleus is what goes into it".
In 1903 Walter Sutton suggested that chromosomes, which segregate in a Mendelian fashion, are hereditary units. Wilson, who was Sutton's teacher, called this the "Sutton–Boveri hypothesis".
Reginald Punnett
Reginald Crundall Punnett FRS (Tonbridge, Kent, 20 June 1875 – Bilbrook, Somerset, 3 January 1967) was a British geneticist. He became Professor of Biology and then Professor of Genetics at the University of Cambridge.
He co-founded, with William Bateson, the "Journal of Genetics" in 1910. Punnett is probably best remembered today as the creator of the Punnett square, a tool still used by biologists to predict the probability of possible genotypes of offspring. His "Mendelism" (1905) is sometimes said to have been the first textbook on genetics; it was probably the first popular science book to introduce genetics to the public.
Reginald Punnett was born in 1875 in the town of Tonbridge in Kent, England. While recovering from a childhood bout of appendicitis, Punnett became acquainted with Jardine's Naturalist's Library and developed an interest in natural history.
Attending the University of Cambridge, Punnett earned a degree in zoology in 1898, and a masters in 1902. Between these degrees he worked as a demonstrator and part-time lecturer at the University of St Andrews Natural History Department. However, by 1902 Punnett was back at Cambridge working in zoology, primarily the study of nematode worms. It was during this time that he and William Bateson began a research collaboration, which lasted several years.