examples of this are: FWA, a dominant allele in arabidopsis, turned 'off' by transposon regulation elements. The overall effect of this heritable silencing is to delay flowering. BNS, a recessive allele in arabiopsis, hypermethylated via siRNA co-opting of RISC complex, which results in silencing. The overall effect of this is the loss of a putative anaphase promoting complex gene. FLC, the flowering locus C gene, which represses flowering time in arabidopsis, can be partially inactivated by the insertion of a Mu-like element (MULE) into the first intron of the gene, resulting in earlier flowering time. There is also evidence to suggest that trasposons play a more general role than was previously thought in the formation of miRNAs as well as in the silencing of centromeres. Parasitism Though the majority of information on transposons is in relation to their parasitic effect, it is sometimes unclear as to how exactly they hurt the host organism. To clarify, there are several ways in which a negative effect can be produced by transposable elements. Production of siRNA or miRNA that target specific cellular mRNAs, resulting in their destruction or inhibiting their translation through an RNAi-related mechanism Production of siRNA or miRNA that stimulates in RNA-Directed DNA Methylation (Rdrm) silencing of a similarly coded gene Insertion into a specific gene, interrupting its normal function Any one of these can have an extreme or minimal effect, depending on what systems the mutation affects. For example, if a transposon were to interrupt the coding for the enzyme which allows for seeds to digest the nourishing endosperm, then the seed would fail to propagate at all, meaning that the mutation was, in essence, fatal. As a counter example, a transposon could be inserted into a non-coding region (which is likely the remnant of a now inactive transposon) and have no effect at all. Future Research Very little is known about the initiation of epigenetic silencing of transposable elements, and aside from the rare exception to this rule, as in the gene Muk, present as an initiator of regulatory epigenetic modification in maize, there are many other unclear aspects of how transposons are regulated in plant genomes. Might they be a first step in evolution that we never knew about? [1] Might they be, simply, a kink in the chain of genetic coding, one that will eventually be worked out? Again, given the lack of information it is hard