Genetics Volume 7

Genetics Volume 7

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 edition. Excerpt: ...middle of the count. The mutation probably occurred in a maternal X chromosome not many divisions prior to maturation. Both yellows were inherited as sex-linked recessives, and by crossing were shown to be allelomorphs. The determination of the locus of yellow to the left of notch and vermilion has already been discussed. Yellow is a valuable mutant because of the ease and accuracy of its classification, its possible identity with similar mutants in other species, and because it can be used with any other sex-linked mutant. Its viability is fair. Yellow in obscura does not occupy the extreme end position in the chromosome map, but in order to make comparison easier, it is treated as the zero point, and map distance based on linkage is computed in both directions. White (wO The first mutation to white occurred in culture 641, when a whiteeyed male was obtained February 13, 1920, in the second count of the bottle. Since no other white individuals were obtained in later counts, the mutation of a wild-type gene to white must have taken place in one of the X chromosomes of the mother at a late stage. The most conspicuous effect of the gene for white is the color of the compound eye and of the three ocelli. The white eyes have a grayish tinge, due probably to the hairs between the ommatidia, and are more similar in appearance to white flies in D. melanogaster that have an ebony body color than to the ordinary melanogaster white. The striking coloration of the abdomen in males of D. obscura, due to the orange color of the testes, is absent in white males. There is no such effect in the females, as the ovaries do not color the abdomen. White females have not produced offspring when mated to white or to any other males. Whitd (w2) The second mutation to...show more

Product details

  • Paperback | 178 pages
  • 189 x 246 x 10mm | 327g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236633288
  • 9781236633286