Question

What is the difference between a promoter sequence and a consensus sequence? (In regards to initiating transcription)

Answer 1

Promoter sequence is a sequence of nucleotides on DNA to which RNA polymerase binds to initiate transcription of downstream gene.

Consensus means conserved. A consensus sequence is a highly conserved sequence of nucleotides. With regards to consensus sequence, we can talk about any type of sequence. For example a sequence of promoter, operator, terminator, any type of gene like hemoglobin, myoglobin, any proto-oncogene like RAS and even the sequence of amino acids. Any two proteins or any two genes having similar sequence of amino acids and nucleotide respectively are said to be consensus sequence are conserved sequence.

With respect to promoter sequence which takes part in transcription, we say that the sequence of promoter is highly conserved. We meant to say that the sequence of promoter is almost similar in very unrelated organism. For example the sequence of promoter TATA box is very similar in prokaryotes and eukaryotes, despite being enormous differences between the two types of organisms.

To summarise, a promoter is a consensus sequence but not all consensus sequences are promoter.

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