Transcription & Translation MCAT Practice Question
A researcher observes that a point mutation in the promoter region of a bacterial gene reduces transcription by 80%. The mutation alters a critical nucleotide within the -10 box consensus sequence recognized by sigma factor. The cell attempts to compensate by increasing RNA polymerase concentration, but transcription rates remain low. Which of the following best explains why increased polymerase concentration fails to restore normal transcription?
Answer choices
- BThe mutation prevents the formation of the open promoter complex by destabilizing DNA melting
- DThe sigma factor cannot properly recognize and bind to the mutated promoter sequenceCorrect answer
- ARNA polymerase cannot access the ribosome binding site downstream of the promoter
- CIncreased polymerase concentration inhibits ribosomal translation of the transcript
- ERNA polymerase requires a specific transcription factor that is depleted at high polymerase levels
- FThe mutation causes premature termination of the RNA polymerase enzyme itself, preventing functional holoenzyme formation
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