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The chromosome of - trailer sequences which are not...

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The chromosome of E. coli The single chromosome of the common intestinal bacterium E. coli is circular and contains some 4.7 million base pairs. It is nearly 1 mm long, but only 2nm wide. The chromosome replicates in a bidirectional method, producing a figure resembling the Greek letter theta. The promoter is the part of the DNA to which the RNA polymerase binds before opening the segment of the DNA to be transcribed. A segment of the DNA that codes for a specific polypeptide is known as a structural gene . These often occur together on a bacterial chromosome. The location of the polypeptides, which may be enzymes involved in a biochemical pathway, for example, allows for quick, efficient transcription of the mRNAs. Often leader and
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Unformatted text preview: trailer sequences, which are not translated, occur at the beginning and end of the region. E. coli can synthesize 1700 enzymes. Therefore, this small bacterium has the genes for 1700 different mRNAs. Lactose, milk sugar, is split by the enzyme β-galactosidase. This enzyme is inducible, since it occurs in large quantities only when lactose, the substrate on which it operates, is present. Conversely, the enzymes for the amino acid tryptophan are produced continuously in growing cells unless tryptophan is present. If tryptophan is present the production of tryptophan-synthesizing enzymes is repressed....
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