An unusual accumulation of repetitive sequences in the rat genome.

We have found in the rat genomic DNA a fragment 1300 bp long, containing an unusual concentration of members of different repetitive families. Three different repeats were noticed. An Alu-like repeat, homologous to the mouse B1 sequence, was followed by a fragment containing alternating purine-pyrimidine bases as in Z-DNA. Finally, a third repeat was identified, containing 38 TAGA tetranucleotides as described for reptile DNA.