The consensus DNA sequence for a promoter is made up of two sequences that are 7 bp long. If two actual promoters in the genome each differ by 3 bases from the consensus sequence, but at different positions. Which of the following can you conclude about transcription from the two promoters?
A.Transcription levels from the two promoters will be roughly equal.
B.In both cases the transcription will be far too low to tell the difference between them.
C.One of the two will almost certainly show higher levels of transcription but it can't be guessed which one.
D.Not enough information
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B and C have no basis..
A seems plausible because they are the same length although they vary by a few bases, i think by random chance they would be recognized as equally. but it really depends on what kind of protein it is because expression in DNA is highly regulated and not left to chance, so i would say D.
It says that the two promoters differ from the consensus sequence by 3bp, at different positions, so you know the sequences of the two promoters are different. It gives you no info whether one of the two promoters preferentially binds a transcription factor, or a transcription repressor, or whether they bind regulatory proteins equally. So you have no basis to conclude or not conclude A. I would say D also, not enough info.
Actually, the extents to which gene expression is deterministic (i.e., dependent on transcription factor levels) or stochastic (essentially based on random physical processes, such as the chance that a transcription factor present in low number will actually find its way to the target DNA and regulate transcription) is fascinating.