The correlation between rDNA copy number and genome size in eukaryotes.

Both rDNA gene multiplicity and genome size vary widely among eukaryotes. For some time, there has been debate regarding any possible relationship between these two parameters. The present study uses data on genome size and rDNA copy number for 162 species of plants and animals to test the association between genome size and rDNA copy number, and provides the first convincing evidence of a strong positive relationship between the two within and among these two groups of organisms. No simple explanations exist for this relationship, but it is nevertheless of clear relevance from both practical and theoretical perspectives.