Dictyostelium rDNA consists of non-chromosomal palindromic dimers containing 5S and 36S coding regions

Restriction enzyme mapping of snap-back DNA has been used to show that the ribosomal DNA (rRNA genes and spacers) from Dictyostelium discoideum exists as 88 kb (kb=1,000 base pairs) linear palindromic dimers. Analysis of the mobility of total cell DNA in 0.15% agarose gels indicates that the majority of the rDNA is not covalently attached to chromosomal DNA.