In the case of Lymnaea peregra, studies indicate that a dextral gene is expressed during egg formation.

在锥实螺的例子中，研究表明右旋基因是在卵的形成期表达的。

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Butt at one time, handedness (twist direction of the shell) was equally distributed within some snail species that have become predominantly dextral or, in a few species, predominantly sinistral.

然而现在已经变为右旋占多数的蜗牛种类，其旋向性（壳的螺旋方向）一度也曾均衡分布，在某些种类中，甚至左旋曾占优势。 。

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In the case of Lymnaea peregra, studies indicate that a dextral gene is expressed during egg formation;

在锥实螺的例子中，研究表明右旋基因是在卵的形成期表达的；

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