Structure and origin of a novel dimeric retroposon B1-dID

Here we describe a new short retroposon family of rodents. Like the primate Alu element consisting of two similar monomers, it is dimeric, but the lef t and right monomers are different and descend from B1 and ID short retropo sons, respectively. Such elements (B1-dID) were found in the genomes of Gli ridae, Sciuridae, Castoridae, Caviidae, and Hystricidae. Nucleotide sequenc es of this retroposon can be assigned to several structural variants. Phylo genetic analysis of B1-dID and related sequences suggests a possible scenar io of B1-dID evolution in the context of rodent evolution.