Q65.Choose the correct statement.
A. Differential gene expression can occur only at the level of transcription.
B. RNA polymerase binds to the promoter region to initiate transcription.
C. Enhancers regulate transcription.
D. Transcription factors can recognize specific sequences of DNA in heterochromatic region.
E. Post-translational modification occurs in nucleus.
Choose the correct answer from the options given below :
(1) A, D and E Only
(2) B and C Only
(3) B, C and D Only
(4) A, C and E Only
Option (2) B and C only is correct.
B is true: RNA polymerase binds to promoter regions (like TATA box in eukaryotes or -10/-35 in prokaryotes) to initiate transcription by forming the pre-initiation complex. C is true: Enhancers are distal DNA sequences that boost transcription by looping to interact with promoters via mediators and transcription factors.
Statement Analysis
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A incorrect: Differential gene expression occurs at multiple levels—transcription (main), post-transcription (splicing, mRNA stability), translation, and post-translation (e.g., phosphorylation).
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B correct: RNA polymerase holoenzyme recognizes and binds promoters to unwind DNA and start RNA synthesis.
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C correct: Enhancers increase transcription rates regardless of position/orientation, often tissue-specific.
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D incorrect: Transcription factors bind accessible euchromatin; heterochromatin is condensed and transcriptionally inactive/silent.
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E incorrect: Post-translational modifications (e.g., glycosylation, ubiquitination) occur in cytoplasm/ER/Golgi, not nucleus (transcription/RNA processing site).
Option Breakdown
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(1) A, D, E: Wrong—A false, D false (heterochromatin inaccessible), E false (PTM not nuclear).
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(2) B, C: Correct—Both verified mechanisms of transcription initiation/control.
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(3) B, C, D: Wrong—D false; TFs can’t access heterochromatic DNA sequences effectively.
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(4) A, C, E: Wrong—A false (multi-level regulation), E false (wrong cellular location).
Introduction to RNA Polymerase Promoter Enhancers Transcription
RNA polymerase promoter enhancers transcription factors heterochromatin tests eukaryotic gene regulation for NEET/CSIR exams. Q65 asks to identify correct statements among options on transcription initiation, enhancers, and chromatin. B and C only are accurate: RNA polymerase binds promoters; enhancers regulate transcription.
RNA Polymerase-Promoter Binding
RNA polymerase II (Pol II) binds core promoters via TBP/TFIID recognizing TATA box (-25 bp upstream), forming PIC with TFII factors. Sigma factor aids bacterial RNAP at -10/-35 boxes. Binding unwinds ~14 bp “transcription bubble” for initiation.
Enhancer Regulation Role
Enhancers (100-1000 bp) contain TF binding sites, loop to promoters via cohesin/mediator, activating Pol II via chromatin remodeling. Position-independent; super-enhancers drive cell identity genes. Confirming statement C.
Why Other Statements Fail
A: Regulation spans chromatin (histone mods), RNA processing, mRNA export/degradation, translation efficiency, protein stability.
D: Heterochromatin (H3K9me3/HP1) silences genes; TFs bind open euchromatin.
E: PTMs like phosphorylation occur post-translation in cytosol/organelles; nucleus handles co-transcriptional RNA mods.
Exam Options Table
Gene Regulation Key Takeaways
Mastering RNA polymerase promoter enhancers transcription factors heterochromatin distinguishes exam success. B+C focus on initiation/control fundamentals vs. common distractors like single-level regulation myths.
