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Unformatted text preview: Once the protein has been completely synthesized, it is removed from the ribosome for further processing. For example, the protein may be stored in the Golgi body of a eukaryotic cell before release, or a bacterium may release it as a toxin. The mRNA molecule is broken up and the nucleotides are returned to the nucleus. The tRNA molecules return to the cytoplasm to unite with fresh molecules of amino acids, and the ribosome awaits the arrival of a new mRNA molecule. Gene control. The process of protein synthesis does not occur constantly in the cell, but rather at intervals followed by periods of genetic silence. Thus, the process of gene expression is regulated and controlled by the cell. The control of gene expression can occur at several levels in the cell. For example, genes rarely operate during mitosis. Other levels of gene control can occur at transcription, when certain operate during mitosis....
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- Fall '07