Transcription, translation and replication are central topics of molecular biology. Nearly all basic statements are founded on studies of the intestinal bacterium Eschericia coli and its parasites, the bacteriophages. Additional insights were gained by the study of other viruses like the tobacco mosaic virus (TMV).
Whether viruses are living is an often asked question. The answer is no. Neither are they precursors of living creatures. They lack a metabolism of their own and are dependent on the machinery of living cells in order to multiply. But they do contain genetic information of their own (stored as DNA or RNA). And if you want to understand genetic information, its storage, replication and expression then viruses are excellent specimen.
It was not before the second research phase (70th till today) that the processes replication and expression were also studied in eucaryotic - including plant - cells. These studies showed that the genetic mechanisms of viruses and procaryotes differ from those of eucaryotes merely in details:
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Many, though not all eucaryotic genes are spliced, i.e. the genetic information is not stored as a continuous piece of DNA but is spread over several segments. |
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The length of the transcription units is very heterogeneous. Eucaryotic transcripts are restructured considerably after transcription. |
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The mechanisms of regulation of transcription and translation are unlike. The respective enzymes and other structural components differ in number, size and specificity. |
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Transcription and translation occur in eucaryotic cells usually in separate compartments (nucleus, cytosol). |
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In eucaryotes the nucleus is not the single place where genetic information is stored. Additional information (DNA) can be found in mitochondria and in the plastids of plants. |
© Peter v. Sengbusch - b-online@botanik.uni-hamburg.de