Apentix/AP Biology/Unit 6: Gene Expression and Regulation/Question
AP Biologyhardmcq1 pt

A point mutation shifts a bacterial promoter's minus 10 hexamer several positions away from the consensus sequence. What direct consequence should be predicted?

A.Sigma factor recognizes the promoter less efficiently, reducing how often RNA polymerase initiates transcription
B.Finished mRNAs acquire extra guanines at their 5' ends
C.Ribosomes stall at the mutated sequence before translating downstream codons
D.Repair enzymes restore the ancestral base before any transcript is initiated

Explanation

Core Concept

Sigma factor contacts conserved promoter elements using the precise arrangement of exposed bases. Deviating from consensus loosens that fit, so fewer holoenzymes settle at the start site per unit time. Initiation frequency falls while elongation machinery and translation remain untouched.

Correct Answer

ASigma factor recognizes the promoter less efficiently, reducing how often RNA polymerase initiates transcription

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