Intraspecific length heterogeneity of the rDNA-IGR in Arabidopsis thaliana due to homologous recombination.

A new heterogeneity of the rDNA spacer of Arabidopsis thaliana, resulting from variation in copy number of the so-called 'C' repeat located downstream of the presumptive polymerase I promoter, is reported. Variation is shown to occur within and between ecotypes. PCR analysis and sequence comparison suggests that the observed length heterogeneity is due to homologous recombination.