DNA transposons], these employ a strategy by which the transposon is excised from its position via transposase, and re-integrated elsewhere in the genome. These can be identified by the following: TIRs, terminal inverted repeats, which allow transposase to recognize the transposon and excise/reintegrate it TSDs, target site duplications, which are generated during re-integration and are thought to add to the difficulties in recognizing transposons Those DNA transposons lacking the coding necessary to synthesize transposase function non-autonomously, likely piggy-backing off of the machinery generated by neighboring transposons of the same class. An example of this would be MITEs, miniature inverted repeat transposable elements, which, while having both TIRs and TSDs, cannot produce transposase. These are particularly prevalent in plants, and are thought to be derived from deletions in the more autonomous DNA transposons. Similarly, these types of transposons can become non-autonomous by capturing or replicating pieces of host DNA. Helitrons Another variety of transposons, discovered in 2001, which can also potentially capture host DNA. Helitrons are thought to replicate via a "rolling circle", in which transposase links the helitron to two distinct regions of the genome at once, using a helicase, ligase, and nuclease in the process to unravel the strands involved, replicate the helitron, and subsequently ligate the replicated material into the new site. During this process, it is thought that the helitrons often encode for the surrounding DNA and integrate this into their own material. Non-autuonomous helitrons may lack a transposase, a helicase, a ligase, or a nuclease. All are thought to be necessary for this complex process of transposition. Silencing of Transposons in Plants Due to their invasive nature, and their potentially disruptive production of ncRNAs, most transposons are dangerous to plants and metazoans alike. Given the lack of distinction between germ-line and somatic cells in the plant kingdom, this is doubly so, since alterations to the genetic and epigenetic code will be more easily inherited. While transposable elements may affect any number of different cell-types in an animal, be a skin cell, a liver cell, a brain cell, these changes are not heritable, due to the fact that an animal inherits only a parents gametic genetic code. In plants, however, there is no such distinction; a flower develops from a meristem, which is a form of somatic cell, and which will pass down to the flower, and thus to the offspring, any genetic or epigenetic alteration. Since