Freeman Gary, Lundelius Judith W
Department of Zoology, University of Texas at Austin, 78712, Austin, Texas, USA.
Wilehm Roux Arch Dev Biol. 1982 Mar;191(2):69-83. doi: 10.1007/BF00848443.
The genetics of body asymmetry inLymnaea peregra follows a maternal mode of inheritance involving a single locus with dextrality being dominant to sinistrality. Maternal inheritance implies that all members of a brood have the same phenotype, however, some broods contain a few individuals of opposite coil. One purpose of this paper is to explain the origin of these anomalous individuals. Genetic analyses of sinistral broods with a few dextral individuals have led to the development of a cross-over model, with the anomalous dextrals originating as a consequence of crossing over either during meiosis or mitosis in the female germ line. The crossover either reconstitutes the dextral gene from previously dissociated parts, or creates a dextral gene by means of a position effect. The probability of a crossover event depends upon the appropriate combination of complementary sinistral chromosomes. Each crossover event has the potential of creating a unique dextral gene. Genetic analyses of dextral broods containing a few sinistral individuals have demonstrated that different dextral genes vary in penetrance.The dextral gene produces a product during oogenesis which influences the pattern of cleavage in the embryo; this cleavage pattern is translated into the appropriate body asymmetry. The other purpose of this paper is to provide an assay for this gene product. Cytoplasm from dextral eggs injected into uncleaved sinistral eggs causes these eggs to cleave in a dextral pattern. Cytoplasm from sinistral eggs has no effect on the cleavage pattern of dextral eggs. While the dextral gene product is made during oogenesis, it does not function in controlling cleavage until just before this process begins.
椎实螺身体不对称的遗传遵循母系遗传模式，涉及一个位点，右旋对左旋呈显性。母系遗传意味着一窝中的所有个体都具有相同的表型，然而，一些窝中包含少数左旋个体。本文的一个目的是解释这些异常个体的起源。对含有少数右旋个体的左旋窝进行遗传分析，得出了一个交叉模型，异常的右旋个体是由于雌性生殖系减数分裂或有丝分裂期间的交叉而产生的。交叉要么从先前分离的部分重新构建右旋基因，要么通过位置效应产生一个右旋基因。交叉事件的概率取决于互补左旋染色体的适当组合。每个交叉事件都有可能产生一个独特的右旋基因。对含有少数左旋个体的右旋窝进行遗传分析表明，不同的右旋基因在 penetrance 上有所不同。右旋基因在卵子发生过程中产生一种产物，该产物影响胚胎的卵裂模式；这种卵裂模式转化为适当的身体不对称。本文的另一个目的是提供对这种基因产物的检测方法。将右旋卵的细胞质注入未分裂的左旋卵中会导致这些卵以右旋模式分裂。左旋卵的细胞质对右旋卵的卵裂模式没有影响。虽然右旋基因产物在卵子发生过程中产生，但直到这个过程开始前它才在控制卵裂中起作用。
