An inbred line of the M' strain Muller-5 Birmingham was studied for its abilities to affect P-M hybrid dysgenesis. This strain possesses 57 P elements, all of which are apparently defective in the production of the P transposase. In combination with transposase-producing elements, these nonautonomous elements can enhance or diminish the incidence of hybrid dysgenesis, depending on the trait that is studied. Dysgenic flies that have one or more paternally-derived chromosomes with these elements partially repress the instability of the P element insertion mutation, sn w; however, such flies have elevated frequencies of another dysgenic trait, GD sterility, and also show distorted segregation ratios. An explanation is presented in which all of these phenomena are unified as manifestations of the kinetics of P element activation in the germ line. The progeny of Muller-5 Birmingham females exhibit partial repression of both sn w instability and GD sterility. This repression appears to involve a factor that can be transmitted maternally through at least two generations. This mode of repression therefore conforms to the pattern of inheritance of the P cytotype, the condition that brings about nearly total repression of P element activity in some strains. Models in which this repression could arise from the nonautonomous P elements of Muller-5 Birmingham are discussed.
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机译：研究了M'菌株Muller-5伯明翰的近交系影响P-M杂种胚发生的能力。该菌株具有57个P元素，所有这些元素显然在P转座酶的生产中都是有缺陷的。与产生转座酶的元件结合，这些非自主元件可以增强或减少杂种发育不全的发生率，具体取决于所研究的性状。具有一个或多个父本染色体且具有这些元件的发育不全的果蝇部分抑制P元件插入突变sn w 的不稳定性；然而，这种果蝇具有另一种致歉性状GD的不育频率，并且显示出畸变的分离比。提出了一种解释，其中所有这些现象都统一为种系中P元素激活的动力学表现。 Muller-5伯明翰雌性的后代对sn w 的不稳定性和GD不育表现出部分抑制作用。这种抑制似乎涉及一个可以在母体中传播至少两代的因素。因此，这种抑制模式与P细胞型的遗传模式相符，在某些菌株中，该条件几乎完全抑制了P元素的活性。讨论了其中这种抑制可能源自Muller-5伯明翰的非自治P元素的模型。
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