Seperack P, Slatkin M, Arnheim N
Department of Biochemistry, State University of New York, Stony Brook 11794.
Genetics. 1988 Aug;119(4):943-9. doi: 10.1093/genetics/119.4.943.
Members of the rDNA multigene family within a species do not evolve independently, rather, they evolve together in a concerted fashion. Between species, however, each multigene family does evolve independently indicating that mechanisms exist which will amplify and fix new mutations both within populations and within species. In order to evaluate the possible mechanisms by which mutation, amplification and fixation occur we have determined the level of linkage disequilibrium between two polymorphic sites in human ribosomal genes in five racial groups and among individuals within two of these groups. The marked linkage disequilibrium we observe within individuals suggests that sister chromatid exchanges are much more important than homologous or nonhomologous recombination events in the concerted evolution of the rDNA family and further that recent models of molecular drive may not apply to the evolution of the rDNA multigene family.
一个物种内rDNA多基因家族的成员并非独立进化，而是以协同的方式共同进化。然而，在不同物种之间，每个多基因家族确实是独立进化的，这表明存在一些机制，能够在种群内部和物种内部扩增并固定新的突变。为了评估突变、扩增和固定发生的可能机制，我们测定了五个种族群体以及其中两个群体内个体的人类核糖体基因中两个多态性位点之间的连锁不平衡水平。我们在个体中观察到的显著连锁不平衡表明，在rDNA家族的协同进化中，姐妹染色单体交换比同源或非同源重组事件重要得多，并且进一步表明，最近的分子驱动模型可能不适用于rDNA多基因家族的进化。
