The analysis of a case of continuous variation in Drosophila by a study of its linkage relations
The analysis of a case of continuous variation in Drosophila by a study of its linkage relations
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DOI：
10.1086/279446
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发表时间：
1914-01-01
影响因子：
2.9
通讯作者：
Dexter, JS
中科院分区：
文献类型：
--
作者：
Dexter, JS
正在考虑的特征是果蝇中的串珠翅膀。正常翅膀（图 1）与图 1 和图 1 所示的形状之间的所有形状等级。 2 至 12 种出现在母种瓶中，尽管某些选定的母种菌株没有产生正常翅膀的后代。当串珠果蝇与其种质中不携带串珠基因的蝇类交配时，F1 后代中串珠的比例会有所不同。如果父本是珠状的，则大多数珠状后代通常是雌性；如果母本是串珠，则大多数串珠后代通常是雄性。然而，雌性串珠蝇比雄性串珠蝇产下更多的串珠子蝇。无论特定的珠蝇是来自雄性还是雌性珠蝇亲本，这种现象都会一代又一代地重复，这表明这种现象不是由性别连锁基因引起的。这种现象并不是由性连锁基因的不分离引起的，因为对 Beaded 和 Wild 种群的测试表明，不分离是一种罕见的现象。唯一的解释是，雄性后代在某种程度上受到卵子带来的细胞质性质的影响或远离珠状，而雌性后代则不容易受到这种影响。对 F2 代的研究表明，大多数正常 F1 后代在遗传上与大多数串珠 F1 后代不同，因为正常果蝇在 F2 代中产生的串珠后代比串珠果蝇少。串珠翅膀与任何性别相关的角色没有任何联系。珠状果蝇与基因位于第二染色体上的性状的果蝇杂交的 F1 代中，大约有一半的果蝇在下一代中显示出与第二染色体性状的连锁，而一半的果蝇则没有显示出这种连锁。未发生连锁的情况下，珠状后代的百分比略低于存在连锁的情况。对这些现象的解释是，在第二条染色体上有一个基因，这里称为 1，它是隐性的，但在杂合条件下，强化了另一个基因，称为 B'，它不在第二条染色体上的显性基因。该基因 1 作为致命因子，阻止任何携带该基因的纯合状态果蝇的发育。具有由第三染色体中的基因引起的性状的果蝇与串珠果蝇杂交的所有F1后代在下一代中都显示出串珠翅与第三染色体性状之间的连锁。这表明第三条染色体上有一个与珠状翅膀发育有关的非致死基因。该基因被称为B'。该基因被证明是生产串珠翅膀的重要生发因子。它有时是显性的，有时是隐性的。决定B'是显性还是隐性似乎有几种可能：一是卵细胞质的性质；二是卵子细胞质的性质。 2d，基因1的存在与否； 3d、自然环境条件。参考环境条件，结果显示，当培养物潮湿时，F1代具有串珠翅的比例高于干燥培养物时；当食物呈碱性时比酸性时更多。没有发现其他影响串珠翅膀生产的环境因素。对或多或少极端的珠状苍蝇的选择很快就会使后代的平均珠状朝着选择的方向移动，但这……
The character under consideration is that of Beaded wings in Drosophila ampelophila. All gradations of form between that of normal wings (Fig. 1) and those shown in Figs. 2 to 12 occur in the stock bottles, though certain selected strains of the stock give no normalwinged offspring. When a Beaded fly is mated to a fly of a stock not carrying genes for Beadedness in its germ plasma varying percentage of the F1offspring is Beaded. If the male parent is Beaded the majority of the Beaded offspring are usually females; and if the female parent is Beaded, the majority of the Beaded offspring are usually males. A female Beaded fly however gives a larger percentage of Beaded daughters than does a male Beaded fly. This phenomenon is repeated from generation to generation, no matter whether a given Beaded fly has come from a male or female Beaded parent, and this shows that the phenomenon is not caused by a sex-linked gene. This phenomenon is not caused by non-disjunction of a sex-linked gene, for tests of both the Beaded and Wild stocks showed non-disjunction to be a rare phenomenon. The only explanation suggested was that the male offspring were somewhat influenced to or away from Beadedness by the nature of the cytoplasm that was brought in with the egg, while females were not readily influenced in this way. A study of the F2generation shows that the majority of the normal F1offspring differ from the majority of the Beaded F1offspring genetically in that normals give fewer Beaded offspring in the F2generation than do the Beaded flies. Beaded wings showed no linkage to any sex-linked character. Approximately one half of the flies of the F1generation of a cross between Beaded flies and flies with characters whose genes were in the second chromosome, showed linkage in the following generation to second chromosome characters, while one half of the flies did not show such linkage. The cases where linkage did not occur gave a slightly lower percentage of Beaded offspring than did those where linkage was present. An explanation of these phenomena is sought in the suggestion that there was in the second chromosome a gene, here called 1, that was recessive but that in the heterozygous condition intensified the dominance of another gene, called B', which was not in the second chromosome. This gene 1 behaves as a lethal factor preventing the development of any fly that carries it in a homozygous condition. All of the F1offspring of the crosses of Beaded flies by flies with characters caused by genes in the third chromosome showed linkage in the following generation between Beaded wings and the third chromosome characters. This was taken to signify that there was in the third chromosome a non-lethal gene concerned in the development of Beaded wings. This gene was called B'. This gene was shown to be the essential germinal factor in the production of Beaded wings. It is sometimes dominant and sometimes recessive. The determination as to whether B' should be dominant or recessive seems to lie in several possibilities: 1st, the nature of the egg cytoplasm; 2d, the presence or absence of the gene 1; 3d, the nature of the environmental conditions. With reference to environmental conditions, it was shown that a larger percentage of the F, generation had Beaded wings when the culture was wet than when it was dry; and more when the food was alkaline than when it was acid. No other environmental factors were discovered which influenced the production of Beaded wings. Selection of more or less extreme Beaded flies very quickly moves the average Beadedness of the offspring in the direction of the selection, but this …