Contributions Volume 21

Contributions Volume 21

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 edition. Excerpt: ...to the other. In a few instances the separation seems to be complete. The blank spaces in these "hyphenated" chromosomes may well be weak spots where under certain conditions breaks occur. As I have not yet determined the nature of these clear intervals in the chromosomes, for the sake of analysis, in this paper, all the separate chromatic bodies are considered as individual chromosomes. Since the chromosomes are small and have no marked characteristics by which they may be recognized, measurements have to be resorted to. Some interesting results have been the outcome. I. The total of the chromosome lengths of any complex whether it has the normal or higher number of chromosomes is the same. This indicated that no chromosomes have been added. 2. IVIIH the fifteen chromosomes of the normal complex are arranged according to decreasing length it is found that they _ exist in a series of seven pairs plus one unpaired chromosome. Each pair differs from the pairs longer and the next shorter pair by almost precisely the same amount--nine per cent. 3. Since such exact relations exist between the normal pairs alteration in any of the chromosomes would destroy these conditions. This was found to be true in cells possessing more than fifteen chromosomes. Comparison with the standard lengths and relationships determined for the chromosomes of the normal complexes made it possible to reunite, with fair accuracy, the fragments to the chromosomes from which they had broken. This reunion has shown that it was chiefly the longer chromosomes that wereconcerned in fragmentation. 4. In the germ cells, the telophase chromosomes of the first maturation division are favorable for study. Two classes of cells are produced by this division, one of which...show more

Product details

  • Paperback | 184 pages
  • 189 x 246 x 10mm | 340g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236952707
  • 9781236952707