Consensus Sequences When analyzing DNA sequences of important genetic elements such as genes and promoters, it becomes clear that cells can use DNA sequences that do the same thing, but are slightly different in the actual sequence. A good example of this is a promoter. The promoter is the region of DNA that is used as a binding and start position for RNA polymerase during transcription. It turns out that the sequence of DNA used in promoters varies between promoters in any particular species and in addition between promoters for similar genes in different bacteria. It is time consuming to report every promoter sequence observed, so scientists will use a consensus sequence to define an overall sequence of a promoter (or genes, or whatever sequence they are studying). Consensus sequences are sometimes thought of as the “average” sequence, although it is better thought of as the most likely sequence you would observe if you analyzed a new promoter. Determining a consensus sequence is actually a simple process.
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