Transcription and RNA Processing

ID #2037

Which of the following 5'-3' sequences is most likely to be recognized by the sigma factor? Incorrect: ATGCAT Correct: TTGTCA Incorrect: GATGGC Incorrect: TTCTTG Incorrect: ATGGAA For this post lecture question, why is TTGTCA the correct answer? I don't understand what makes the sequence recognizable by the sigma factor. One of your previous posts stated that the more it deviates from the expected sequence the less likely. I thought I understood because TTCTTG(my answer) doesn't seem to deviate as much as TTGTCA.

E. coli sigma factor is looking for two different things: TTGACA and TATAAT. Since this question doesn't tell you which, it could be either. Look at the "correct" answer to the question. TTGTCA differs from TTGACA at only one position, but TTCTTG differs from TTGACA at 4 of the 6 positions, almost a total mismatch. If you're sigma factor, and you're looking for TTGACA, you're not very likely at all to stop at TTCTTG, wouldn't you say?

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