Epigenetic regulation of transposable elements in the plant kingdom which allows for self-copying) within the coding of the transposon defines class I elements as autonomous or non-autonomous. Class I transposons can take the form of: Curiously, retrotransposons have been discovered to be the predominant form of transpositional element in plants with large genomes, such as maize and wheat, potentially indicating rapid success of this class of transposon in the creation of hybrids, such as wheat, peppermint and, in the distant past, maize. Plant hybridization often creates polyploids, with double, triple, quadruple or more the number of chromosomes present in the parent generation. Polyploid hybrids seem to be particularly susceptible
Owned-and-operated television stations in the United States its partnership, in November 1993 (fourteen months before the network debuted), Tribune agreed to a deal to affiliate most of its independent stations with The WB. Despite Tribune's minority stake, the company's stations were not considered to be WB owned-and-operated-stations due to Time Warner's controlling interest in the network. This resulted in The WB having the unusual distinction of being the only broadcast network that did not have O&Os in New York City, Los Angeles and Chicago throughout its existence (the three Tribune-owned WB affiliates in those cities – WPIX, KTLA and WGN-TV, respectively – were "affiliates" of the network