Brookfield John F Y, Johnson Louise J
Institute of Genetics, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK.
Genetics. 2006 Jun;173(2):1115-23. doi: 10.1534/genetics.104.027219.
Some families of mammalian interspersed repetitive DNA, such as the Alu SINE sequence, appear to have evolved by the serial replacement of one active sequence with another, consistent with there being a single source of transposition: the "master gene." Alternative models, in which multiple source sequences are simultaneously active, have been called "transposon models." Transposon models differ in the proportion of elements that are active and in whether inactivation occurs at the moment of transposition or later. Here we examine the predictions of various types of transposon model regarding the patterns of sequence variation expected at an equilibrium between transposition, inactivation, and deletion. Under the master gene model, all bifurcations in the true tree of elements occur in a single lineage. We show that this property will also hold approximately for transposon models in which most elements are inactive and where at least some of the inactivation events occur after transposition. Such tree shapes are therefore not conclusive evidence for a single source of transposition.
一些哺乳动物散布重复DNA家族，如Alu短散在元件序列，似乎是通过一个活性序列被另一个活性序列的连续替代而进化的，这与存在单一转座源：“主基因”相一致。多个源序列同时活跃的替代模型被称为“转座子模型”。转座子模型在活跃元件的比例以及失活是发生在转座时还是之后方面存在差异。在这里，我们研究了各种类型的转座子模型对于在转座、失活和缺失达到平衡时预期的序列变异模式的预测。在主基因模型下，元件真实树中的所有分支都发生在单个谱系中。我们表明，对于大多数元件不活跃且至少一些失活事件发生在转座之后的转座子模型，这一特性也将大致成立。因此，这种树形并不是转座单一源的决定性证据。
