inverted repeats of the transposon and mediate synapsis of the transposon ends. The transposase enzyme then disconnects the element from the flanking DNA of the original donor site and mediates the joining reaction that links the transposon to the new insertion site. The addition of the new DNA into the target site causes short gaps on either side of the inserted segment. Host systems repair these gaps resulting in the target sequence duplication (TSD) that are characteristic of transposition. In many reactions, the transposon is completely excised from the donor site in what is called a "cut and paste" transposition and inserted into the target DNA to form a simple insertion. Occasionally, genetic material not originally in the transposable element gets copied and moved as well. Helitrons Helitrons are also a group of eukaryotic class II TEs. Helitrons do not follow the classical "cut and paste" mechanism. Instead, they are hypothesized to move around the genome via a rolling circle like mechanism. This process involves making a nick to a circular strand by an enzyme, which separates the DNA into two single strands. The initiation protein then remains attached to the 5' Phosphate on the nicked strand, exposing the 3' hydroxyl of the complementary strand. This allows a polymerase enzyme to begin replication on the un-nicked strand. Eventually the entire strand is replicated at which point the newly synthesized DNA disassociates and is replicated in parallel with the original template strand. Helitrons encode an unknown protein which is thought to have HUH endonuclease function as well as 5' to 3' helicase activity. This enzyme would make a single stranded cut in the DNA which explains the lack of Target Site Duplications found in Helitrons. Helitrons were also the first class of transposable elements to be discovered computationally and marked a paradigm shift in the way that whole genomes were studied. Polintons Polintons are also a group of eukaryotic class II TEs. As one of the most complex known DNA transposons in eukaryotes, they make up the genomes of protists, fungi, and animals, such as the entamoeba, soybean rust, and chicken, respectively. They contain genes with homology to viral proteins and which are often found in eukaryotic genomes, like polymerase and retroviral integrase. However, there is no known protein functionally similarly to the viral capsid or envelope proteins. They share their many structural characteristics with linear plasmids, bacteriophages and adenoviruses, which