THE MOLECULAR-STRUCTURE, CHROMOSOMAL ORGANIZATION, AND INTERSPECIES DISTRIBUTION OF A FAMILY OF TANDEMLY REPEATED DNA-SEQUENCES OF ANTIRRHINUM-MAJUS L

Monomers of a major family of tandemly repeated DNA sequences of Antir rhinum majus have been cloned and characterized. The repeats are 163-1 67 bp long, contain on average 60% A+T residues, and are organized in head-to-tail orientation. According to site-specific methylation diffe rences two subsets of repeating units can be distinguished. Fluorescen t in situ hybridization revealed that the repeats are localized at cen tromeric regions of six of the eight chromosome pairs of A. majus with substantial differences in array size. The monomeric unit shows no ho mologies to other plant satellite DNAs. The repeat exists in a similar copy number and conserved size in the genomes of six European species of the genus Antirrhinum. Tandemly repeated DNA sequences with homolo gy to the cloned monomer were also found in the North American section Saerorhinum, indicating that this satellite DNA might be of ancient o rigin and was probably already present in the ancestral genome of both sections.