A biology-oriented view on genome evolution.

The Dynamic Nature of Eukaryotic Genomes

Laura Wegener Parfrey,* Daniel J. G. Lahr,* and Laura A. Katz*

*Program in Organismic and Evolutionary Biology, University of Massachusetts; and
Department of Biological Sciences, Smith
College, Northampton, MA

Analyses of diverse eukaryotes reveal that genomes are dynamic, sometimes dramatically so. In numerous lineages
across the eukaryotic tree of life, DNA content varies within individuals throughout life cycles and among individuals
within species. Discovery of examples of genome dynamism is accelerating as genome sequences are completed from
diverse eukaryotes. Though much is known about genomes in animals, fungi, and plants, these lineages represent only
3 of the 60–200 lineages of eukaryotes. Here, we discuss diverse genomic strategies in exemplar eukaryotic lineages,
including numerous microbial eukaryotes, to reveal dramatic variation that challenges established views of genome
evolution. For example, in the life cycle of some members of the ‘‘radiolaria,’’ ploidy increases from haploid (N) to
approximately 1,000N, whereas intrapopulation variability of the enteric parasite Entamoeba ranges from 4N to 40N.
Variation has also been found within our own species, with substantial differences in both gene content and chromosome
lengths between individuals. Data on the dynamic nature of genomes shift the perception of the genome from being fixed
and characteristic of a species (typological) to plastic due to variation within and between species.