File:Contributions to the genetics of Drosophila melanogaster (1919) (20502640339).jpg

Title: Contributions to the genetics of Drosophila melanogaster
Identifier: contributionsto00carn (find matches)
Year: 1919 (1910s)
Authors: Carnegie Institution of Washington; Morgan, Thomas Hunt, 1866-1945; Bridges, Calvin B. (Calvin Blackman), 1889-1938; Sturtevant, A. H. (Alfred Henry), 1891-1970
Subjects: Drosophila melanogaster; Heredity; Karyokinesis
Publisher: Washington, Carnegie Institution of Washington
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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58 THE ORIGIN OF GYNANDROMORPHS. Doncaster's observations on binucleated eggs of Abraxas, where both nuclei underwent separate reduction and fertihzation, ofifer a simpler explanation. On the other hand, it should be pointed out that there should have been at least as many autosomal mosaics as sex-linked mosaics produced by fertilization of binucleated eggs of heterozygous mothers; and this does not seem to be the case. No. B. 90. June 17, 1912. C. B. Bridges. Text-figure 48 (drawing). Parentage.—This gynandromorph appeared in F2 from the cross of rudimentary female to white miniature male; that is, the mother (F, female) carried rudimentary in one X and white and miniature in the other; and the father was a rudimentary (Fi) male. Description.—The individual seemed to be male through- out. Both eyes were red. Sex-combs were present on both forelegs. The right wing was long, and though slightly deformed, was undoubtedly wild-type. The left wing was a typical and perfect miniature rudimentary wing. The abdomen was entirely male, and when mated to a vermilion female the fly bred as a male, producing abundant offspring. Several pairs of the wild-type daugh- ters and vermilion sons of this mating were bred and all produced red and vermilion in equal numbers, both in males and females. That is, the gynandromorph bred as a wild- type male carrying no mutant genes. Two of the F2 pairs are given as samples:
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Text-figure 48. Wild-type 9 Wild-type (f Vermilion 9 Vermilion cT B. 98.1 B. 98.2 45 26 33 16 32 30 43 33 The drawing has been previously figured in Zeit. f. ind. Abst. und Verer., 1912, p. 324. Explanations.—Simple elimination fails to explain this case, because the characters of the fly, as well as its genetic behavior, show that it received two different X chromosomes from its mother. For instance, miniature and rudimentary were both present in the left (male) wing, which proves that the X contained in these parts came from the mother and that crossing-over in the mother must have occurred. Since the right wing was wild-type, its cells must have contained a wild-type X, which likewise could only have come from the mother. The Fi and F2 offspring of the gynandromorph showed that he had such a wild-type X in the testis, which presumably came from the same kind of cells as those of the right side. The offspring also show that the gynandromorph had not received an X sperm from the father, which would have given rudimentary offspring. Therefore the right side, at least, must have come from a Y-bearing sperm, as further proved by the fact that the gynandromorph was fertile as a male (males without a Y being sterile). On the view that the gynandromorph came from an egg with two nuclei, a simple explanation of the result may be given. Before reduction, each of the postulated nuclei must have had one white miniature X and one red rudimentary X chromosome; after crossing-over and reduction in each, one

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