Electron Microscopic Visualization of Transcription

With the possible exception of DNA-containing cytoplasmic organelles, transcription and trans-lation are compartmentalized in eucaryotic ells. That is, RNA polymerases transcribe nuclear DNA, and the various RNAs involved in translation migrate to the cytoplasm where protein synthesis occurs. On the other hand, in proearyotic ells, transcription and translation occur in the same region of the cell, at the same time, and in a coordinated manner. The transcription process has now been observed in both a eucaryotic ell, the amphibian oocyte (Miller and Beatty,]969a, c), and in a procaryotic cell, the bacterium Escherichia cell (Miller et al., 1970). METHODOLOGY