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Promoters and Sigma Factors

Promoters and Sigma Factors - and thus require different...

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Promoters and Sigma Factors The nucleotide sequence of promoters is similar but not identical. The more similar the sequence is to a consensus sequence, the more likely that RNA polymerase will attach and produce mRNA from the associated genes. Part of the RNA polymerase enzyme that recognizes the promoter is called the sigma factor. After transcription begins, this unit dissociates from the enzyme. Different sigma factors recognize different promoters and thus, the availability of sigma factors can regulate the transcription of genes associated with these promoters. The availability of sigma factors can be used to regulate sets of genes. For example, a group of genes whose product is rarely needed might have a different promoter sequence than other genes
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Unformatted text preview: and thus require different sigma factors. These genes would only be transcribed when the correct sigma factor became available. Example of Translational Control in Prokaryotes: Antisense RNA Normally, mRNA is synthesized off of the template (antisense) strand of DNA. Antisense RNA is synthesized from the noncoding (sense) strand of DNA. The two mRNA molecules bond together, inactivating the mRNA. This mechanism appears to be universal among bacteria. It has not been shown to be a normal means in eukaryotes. Antisense RNA can be injected into eukaryotic cells as a control mechanism....
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