Williams S M, Strobeck C
J Theor Biol. 1985 Oct 21;116(4):625-36. doi: 10.1016/s0022-5193(85)80092-8.
The structures of rDNA spacers from several species have been characterized and virtually all have internally repeated sequences. Different numbers of these internal repeats are responsible for most spacer length variation. Because unequal recombination between these internal repeats will cause new length variation, while unequal exchange between rDNA copies will homogenize the variants, we modeled the interaction of these two processes. Two models were used to simulate both types of unequal exchange at the sister chromatid level. Both models indicate that a narrow range of relative recombination frequencies is required to produce levels of variability comparable to those published. One model puts a lower limit on the number of internal repeats, and the other puts both a lower and upper limit on the number of repeats. The model with both maximum and minimum constraints produces a distribution closer to actual spacer distributions. These results imply that small changes in recombination rates can generate the differences in numbers of length variants observed in different species.
几种物种的核糖体DNA间隔区结构已得到表征，几乎所有间隔区都有内部重复序列。这些内部重复序列数量的不同导致了大多数间隔区长度的变化。由于这些内部重复序列之间的不等位重组会导致新的长度变化，而核糖体DNA拷贝之间的不等位交换会使这些变体同质化，因此我们对这两个过程的相互作用进行了建模。使用两种模型在姐妹染色单体水平上模拟这两种不等位交换类型。两种模型均表明，需要一个较窄范围的相对重组频率才能产生与已发表数据相当的变异水平。一种模型对内部重复序列的数量设定了下限，另一种模型则对重复序列的数量设定了下限和上限。具有最大和最小限制的模型产生的分布更接近实际的间隔区分布。这些结果表明，重组率的微小变化会导致不同物种中观察到的长度变体数量的差异。
