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 owned KTLA (channel 5) in Los Angeles and WBKB (channel 4, now WBBM-TV on channel 2) in Chicago, owned a share of the network. However, the FCC declared that Paramount controlled DuMont and thus forbade the network and the studio from acquiring any more stations. This was one of the factors that led to DuMont shutting down in August 1956. For much of the era from 1958 to 1986, the major network-owned stations were distributed as follows: ABC, CBS and NBC each owned stations in the top three markets (New York City, Los Angeles and Chicago). Between 1958 and 1965,