Levan Albert (5 results)

Pamphlet. Condition: Very Good. pp. 223-251, Photos, Extracted from orig vol, begins with title page, trimmed & stapled, thus is like a pamphlet, editorial marks on title page else VG.

(S. A. Unio Nord. Contra Concrum Symp. on Virus and Cancer) 1964. S. 75 - 94. m. zahlr. Abb. br. -2) Sonderabdruck.

Soft cover. Condition: Good. Lund, 1935. 128 pages. Printed wrappers. The over-sized wrappers are slightly bumped and chipped. Illustrated. Unopened. Offprint from Hereditas XXII.

Hardcover. Condition: Good. Private-bound cloth with slightly red-stained edges, unknown bookbinder. The spine is faded. The off-prints are bound without wrappers unless otherwise stated. Contents: (1) "Zahl und Anordning der Chromosomen in der Meiosis von Allium." From Hereditas XIII. Lund, 1929. Pp. 80-86. Without wrappers. Author's dedication to botanist Arne Hässler. (2) "Experimentell analys och syntes av polyploida arter inom Allium paniculatum-gruppen." From Nordiska (19. Skandinaviska) naturforskarmötet i Helsingfors. 1936. 2 pages. (3) "Polyploidi and Self-Fertility in Allium." From Hereditas XXII. Lund, 1936. Pp. 278-280. (4) "Pseudo-bivalent formation in the pollen of Allium Schoenoprasum". From Botaniska notiser 1937. Pp. 151-152. (5) "Cytological Studies in the Allium Group." From Hereditas XXIII. Lund, 1937. Pp. 317370. Bound with the original wrappers. (6) "Amphibivalent formation in Allium cernuum and its consequences in the pollen." From Botaniska notiser. Lund, 1939. Pp. 256-260. Bound with the original wrappers. (7) "Meiosis of Allium Porrum, a Tetraploid Species with Chiasma Localisation." From Hereditas XXVI. Lund, 1940. Pp. 454-462. (8) "The Cytology of Allium Amplectens and the Occurrence in Nature of its Asynapsis." From Hereditas XXVI. Lund, 1940. Pp. 353-394. Bound with the original wrappers. (9) "Die Zytologie von Allium Cepa x Fistulosum." From Hereditas XXI. Lund, 1936. Pp. 195-214. Bound with the original wrappers. Author's dedication to Arne Hässler (partly cut in the top margin). (10) "The Cytology of the Species Hybrid Allium Cepa x Fistulosum and its Polyploid Derivatives." From Hereditas XXVII. Lund, 1941. Pp. 253-272. Bound with the original wrappers. (11) "Cytological Studies in Allium. A Preliminary Note." From Hereditas XV. Lund, 1931. Pp. 347-356. Author's dedication to Arne Hässler (partly cut in the top margin). (12) "Cytological Studies in Allium, II. Chromosome Morphological Contributions." From Hereditas XVI. Lund, 1932. Pp. 257-294+plate. Bound with the original wrappers. Author's dedication to Arne Hässler. (13) "Cytological Studies in Allium, III. Allium Carinatum and Allium Oleraceum." From Hereditas XVIII:1-2. Lund, 1933. Pp. 101-114+plate. Bound with the original wrappers. Author's dedication to Arne Hässler. (14) "Cytological Studies in Allium, IV. Allium Fistulosum" From Svensk Botanisk Tidskrift. Bd. 27. H. 2. Uppsala, 1933. Pp. 211-232. Bound with the original wrappers. (15) "Cytological Studies in Allium, V. Allium Macranthum" From Hereditas XVIII. Lund, 1933. Pp. 349-359. Author's dedication to Arne Hässler (partly cut in the top margin). (16) "Cytological Studies in Allium, VI. The Chromosome Morphology of some Diploid Species of Allium." From Hereditas XX. Lund, 1935. Pp. 289-330. Bound with the original wrappers. Author's dedication to Arne Hässler. An extensive collection of early off-prints by Levan, later known for establishing the number of chromosomes in the human genome together with Joe Hin Tjio.

Lund, 1956. 4to. Minor signs of wear. A fine copy, With signature of "Joh. Holtfreter" to top of p. (1). 6 pp. + 1 plate. First printing, in the very rare off-print - Johannes Holtfreter's copy -, of the revolutionary paper that established for the first time the correct number of chromosomes in man, thus founding modern human cytogenetics. The present paper constitutes the most important breakthrough in genetics since Mendel. "The finding that the normal human diploid chromosome number was 46, rather than 48 as had been assumed for many years previously, represents the starting point of modern human cytogenetics, with great importance for future clinical applications in the detection of both constitutional chromosome abnormalities and somatic abnormalities such as those seen in cancers. This discovery, made 50 years ago at the Institute of Genetics of the University of Lund, Sweden, in December 1955 and published early in 1956 in the journal "Hereditas" (Tjio and Levan 1956), is now of historical as well as scientific importance." (Harper). "After 50 years, the paper of Tjio and Levan can be clearly seen as one of the major landmarks of human genetics, opening up the field of human chromosomes and of medical genetics generlly to detailed analysis, as well as fulfilling its original aim of providing a normal reference point for studies of chromosomes in cancer." (Harper).The rediscovery of Mendel's law at the end of the 19th century triggered intense interest in the principles of heredity" ever since that time, chromosome behavior had been studied scientifically, but although a great deal of scientific interest was directed towards learning more about chromosomes themselves, it wasn't until Joe Hin Tjio and Albert Levan's epochal discovery that the correct human chromosome count was established. For half a century it had been accepted that humans normally have 48 chromosomes - only due to Tjio and Levan were we to know that the chromosome number of man is actually 46. "Difficulties in determining the human diploid number arose for a variety of reasons. For one, early experiments that provided evidence for the chromosome theory often used invertebrate species that reproduced in large numbers and had a relatively low number of well-defined chromosomes. Neither of these characteristics, of course, is a common finding in humans. In addition, the human samples initially used for chromosome analysis were derived from fresh testicular tissue in which haploid meiotic cells were often present. Furthermore, what morphology could be deduced suggested that human chromosomes were more complex than those of the model organisms studied earlier. In light of these and other factors, an erroneous estimate by prominent cytologist Theophilus Painter dominated the field for decades, until researchers Joe Hin Tjio and Albert Levan eventually applied new technology to identify the true diploid number of human chromosomes." (O'Connor). As Painter's estimate of 48 chromosomes had been generally accepted from studies over the previous 30 years, study of normal human chromosomes was not an active research field in the mid-1950's. Albert Levan - one of the key figures in cancer cytogenetics -, however, extensively studied the chromosomes of human cancers and realized that it was necessary to be certain of the normal human karyotype. Likewise, Joe Hin Tjio - who then was primarily involved in plant cytogenetics - realized the importance and necessity in establishing the correct number. "In the decades following Painter's work, scientists continued to refine their methods for preparing chromosomes for microscopy. Sectioning of paraffin-embedded preserved tissue was gradually replaced by squash techniques, in which small tissue specimens are placed on a microscope slide and then literally squashed under a cover slip to produce a single layer of cells. This approach gained broad acceptance as it eliminated any need to slice through tissues and reconstruct th.