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Modes and Tempos in the Evolution of Nuclear Ribosomal DNA: New Characters for Evolutionary Studies and New Markers for Genetic and Population Studies

Richard A. Jorgensen and Paul D. Cluster
Annals of the Missouri Botanical Garden
Vol. 75, No. 4 (1988), pp. 1238-1247
DOI: 10.2307/2399282
Stable URL: http://www.jstor.org/stable/2399282
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Modes and Tempos in the Evolution of Nuclear Ribosomal DNA: New Characters for Evolutionary Studies and New Markers for Genetic and Population Studies
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Abstract

The tempo of evolutionary change determines in what manner any class of characters is informative in evolutionary studies and at which taxonomic levels. Here we describe and summarize some fundamental features of the evolution of the DNA sequences that encode ribosomal RNA genes in the nuclear genome of higher plants. By analyzing a sample of angiosperm species having known phylogenetic relationships at five different taxonomic levels ranging from the intraspecific to the interfamilial, we show that plant ribosomal DNA determines at least eleven classes of characters that can be distinguished by comparisons at the DNA level. These classes are temporal and physical subsets of three basic modes of variation: length variation, single base pair substitution, and DNA modification. We also discuss the impact of length variants on population genetic studies and the implications of these studies for understanding the molecular mechanisms of rDNA evolution.

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