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arXiv 1209.1445q-bio.PE
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果蝇遗传约束的实验检验

An experimental test for genetic constraints in Drosophila melanogaster

Ian Dworkin, David Tack, Jarrod Hadfield

摘要:

除了自然选择,适应性进化还需要遗传变异。然而,G矩阵可能具有有限的“遗传自由度”,某些特征值的组合无法进化。这种限制通常被称为遗传限制。不幸的是,很少有关于何时会出现约束的明确预测。因此,我们开发了一个实验系统,提供有关约束的具体预测。这些测试是重要的,因为关于遗传限制的证据仍然存在分歧,可能是由于方法学,研究系统或两者的差异。许多遗传约束的措施已被提出,一般集中在一些轴G的特征值=~0,表明缺乏遗传方差。突变Ultrabithorax 1引起一个温和的同源异型转换的体节身份。我们预测,这种突变将导致遗传约束,由于这种同源异型。我们测量了一组具有和不具有Ubx 1的菌株中的一组性状的遗传协变。正如预期的那样,Ubx 1诱导同源异型转化,并改变了异速生长模式。然而,没有变化的相关结构,也没有在G的本征值的分布。我们讨论的作用,利用遗传操作,完善假设的约束,在自然系统中。

英文摘要:

In addition to natural selection, adaptive evolution requires genetic variation to proceed. Yet the G-matrix may have limited 'genetic degrees of freedom', with certain combinations of trait values unavailable to evolution. Such limitations are often referred to as genetic constraints. Unfortunately, clear predictions about when to expect constraints are rarely available. Therefore, we developed an experimental system that provides specific predictions regarding constraints. Such tests are important as disagreements persist regarding the evidence for genetic constraints, possibly due to differences in methodology, study system or both. Numerous measures of genetic constraints have been suggested, and generally focus on whether some axes of G have eigenvalues=~0, indicating a lack of genetic variance.The mutation Ultrabithorax1 causes a mild homeotic transformation of segmental identity. We predicted that this mutation would induce a genetic constraint due to this homeosis. We measured genetic co-variation for a set of traits in a panel of strains with and without Ubx1. As expected, Ubx1 induced homeotic transformations, and altered patterns of allometry. Yet, no changes in correlational structure nor in the distribution of eigenvalues of G were observed. We discuss the role of using genetic manipulations to refine hypotheses of constraints in natural systems.

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