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 opened up a new spectrum of frequencies on the UHF dial (channels 14–83) for terrestrial television. As an incentive for companies to operate UHF stations, the FCC relaxed the ownership limit for a given entity from five to seven stations, provided that no more than five were on the VHF dial. With this opportunity to expand its roster of O&Os, NBC bought WBUF-TV (channel 17) in Buffalo in 1955 and WKNB-TV (channel 30) in New Britain, Connecticut (near Hartford) in 1957, and changed WKNB's call letters to WNBC-TV (the present-day WNBC in New York City used the WRCA-TV callsign from