alleryStart learning →Which promoter element is recognized and bound by the sigma subunit?
AThe TATAAT sequence at -10
BThe TTGACA sequence at -35
CThe initiation site at +1
DThe abortive transcript region
Answer & Solution
Correct answer: B. The TTGACA sequence at -35
1. Sigma gives the polymerase its choice of start site, so it must contact the promoter directly.
2. The sequence it recognizes and binds is TTGACA at -35.
3. Once that contact is made, the subunits of the core enzyme bind to the site.
4. The A and T rich -10 element then facilitates unwinding, so TATAAT matters for opening the helix rather than for recognition.
5. The +1 site is where the first transcript nucleotide is made, not a recognition element.
6. Abortive transcripts are short RNAs released at the close of initiation, so they are a product rather than a promoter element.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 15 "Genes and Proteins", section 15.2 Prokaryotic Transcription_
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