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4.3 Regulation — Test 1
Q1. In E. coli, the trp operon is regulated by:✓ Both attenuation and repression
Q2. Constitutive expression of the lac operon results from a mutation in:✓ lacO (operator) or lacI (repressor)
Q3. The tryptophan operon is best described as:✓ Negatively repressible (repressed by Trp via corepressor)
Q4. Allolactose acts in lac operon regulation as the:✓ Inducer
Q5. Bacteria preferentially use glucose over other sugars through:✓ Catabolite repression
Q6. Catabolite repression in prokaryotes is mediated through:✓ cAMP (and the CAP/CRP activator)
Q7. Differential gene regulation means different cell types express different ___ but share the same ___:✓ proteins; genome
Q8. Enhancer regions are typically characterised by:✓ DNase I hypersensitivity, H3K4me1/2 and p300 binding
Q9. FOS, JUN and MYC are:✓ Genes encoding transcription factors that drive growth-related genes
Q10. Gene transcription is repressed by:✓ Promoter CpG methylation, gene-body methylation effects, etc. — all the listed
Q11. Genes in a polycistronic operon are expressed from:✓ A single promoter
Q12. Excess glucose inhibits lac operon transcription because of low synthesis of:✓ Cyclic AMP
Q13. Histone acetylation increases transcription because:✓ It loosens the DNA-histone interaction, making DNA more accessible
Q14. When E. coli grows in glucose + lactose together:✓ Neither CAP nor repressor is bound
Q15. In mammalian DNA, regulatory regions with CpG islands are inactivated by:✓ Methylation
Q16. The most appropriate definition of an operator is:✓ A regulatory DNA sequence bound by a repressor protein
Q17. In the presence of allolactose, the lac repressor:✓ Cannot bind the operator
Q18. In the NtrB/NtrC two-component system, the sensor kinase is:✓ NtrB
Q19. Inducible genes are transcribed because:✓ The inducer inactivates the repressor
4.3 Regulation — Test 2
Q20. The lysogenic state of phage λ is favoured when:✓ Nutrients are abundant and the cell is healthy (high CII/CIII)
Q21. Pick the correct statement about CAP (catabolite activator protein) in the lac operon:✓ cAMP-CAP binding to the activator site recruits RNA polymerase
Q22. An 'aptamer' sequence that binds a small molecule is found in the:✓ Riboswitch region of mRNA
Q23. Riboswitches regulate gene expression by:✓ Directly binding small molecules to change mRNA secondary structure
Q24. Steroid response elements (SREs) are composed of:✓ Nucleotides (DNA sequences)
Q25. The synthetic Ptac promoter differs from Plac in that Ptac lacks/does not need:✓ A CAP/cAMP-CRP dependence for strong activity (it is a strong hybrid trp-lac promoter)
Q26. TATA boxes and Pribnow boxes are components of which region?✓ Promoter
Q27. A site that controls adjacent genes only on the same DNA molecule (irrespective of alleles) is:✓ Cis-acting site
Q28. Expression of a transgene in target tissue is conveniently identified using a:✓ Reporter gene (e.g. GFP/lacZ/luciferase)
Q29. In the trp operon leader, ribosome stalling at the two contiguous Trp codons (low Trp) allows leader regions to pair so that:✓ The 2:3 antiterminator forms, permitting transcription to continue
Q30. The physical proximity of a distal enhancer to its promoter is measured by:✓ Chromosome conformation capture (3C/Hi-C)
Q31. A repressor inhibits operon expression by binding to the:✓ Operator
Q32. Specific (gene-selective) control of transcription involves DNA-binding motifs such as:✓ All of these
Q33. The tac promoter is an example of a:✓ Hybrid promoter (trp -35 + lac -10)
Q34. The trp operon's transcription-termination-based regulation when tryptophan is abundant is called:✓ Attenuation
Q35. Which transcription activator binds the UAS of the nif promoter?✓ NtrC-P (phosphorylated NtrC)
Q36. Wild-type E. coli shifted from glucose to lactose-only medium will:✓ Induce the lac operon
Q37. 5S rRNA is transcribed outside the nucleolus by:✓ RNA Pol III
Q38. Which is TRUE of the lac operon in E. coli?✓ Its transcription yields a polycistronic mRNA
4.3 Regulation — Test 3
Q39. The lac operon genes are MOST highly expressed under:✓ Low glucose, high lactose
Q40. Which DNA-binding domain is characteristic of steroid hormone receptors?✓ Zinc fingers (C4 type)
Q41. Maximal lac operon expression occurs with:✓ High cAMP, no glucose, and lactose present
Q42. Which factor would INCREASE lac operon transcription?✓ Increased lactose (inducer)
Q43. A characteristic of an inducible operon is that:✓ Expression is triggered by a specific inducer
Q44. Which is NOT a feature of a typical bacterial operon?✓ Genes are translated into a single polypeptide
Q45. Which is NOT a feature of transcription factors?✓ Glycosylation domain
Q46. Which method CANNOT detect lac repressor binding to its operator?✓ Luciferase reporter assay (measures expression, not direct binding here)
Q47. Which mRNA contains an attenuator sequence in its 5' leader?✓ trp operon
Q48. In the presence of glucose:✓ cAMP-CAP binding decreases
Q49. Which promoter depends on the cAMP-CRP complex for activation?✓ Plac
Q50. Which condition switches the lac operon ON?✓ -Glucose, +Lactose
Q51. Which is NOT a bHLH-family protein?✓ Pax1
Q52. Which promoter can be induced simply by raising the culture temperature?✓ Phage λ pL/pR (with a temperature-sensitive cI857 repressor)
Q53. Which regulatory protein can act as BOTH activator and repressor at the same DNA elements?✓ AraC
Q54. Which scenario would NOT cause constitutive lac expression?✓ A promoter that cannot bind RNA polymerase
Q55. Which statement about the nuclear receptor superfamily is NOT true?✓ All nuclear receptors are always cytosolic and never enter the nucleus without ligand
Q56. Which statement about enhancers is correct?✓ Can act at variable distance and orientation from the promoter
Q57. Which λ protein acts as both an activator and a repressor of transcription?✓ cI (the λ repressor)
4.3 Regulation — Test 4
Q58. Which transcription factor acts as both activator and repressor (arabinose system)?✓ AraC
Q59. Active transcription of the yeast GAL1/GAL10 promoters is suppressed by:✓ Glucose
Q60. In E. coli, the heat-shock response is primarily controlled by:✓ σ32 (RpoH)
Q61. Statement: small non-coding RNAs post-transcriptionally regulate bacterial gene expression. Reason: sRNA is complementary to mRNA and binding either blocks or promotes translation. Choose:✓ Both true, R explains S
Q62. Which is responsible for post-transcriptional regulation in bacteria?✓ Small regulatory RNAs (sRNAs)
Q63. Differential gene expression among cell types is achieved mainly by:✓ Selective transcription of different genes
Q64. An insulator element functions to:✓ Block enhancer action on a promoter (or act as a barrier)
Q65. Which is a characteristic of catabolite repression?✓ High glucose lowers cAMP, reducing CAP activation
Q66. The lac repressor is a product of which gene, acting in trans?✓ lacI
Q67. Positive control of an operon means:✓ An activator protein is required to turn it on
Q68. The bacterial enhancer-like UAS elements for σ54 promoters require:✓ A bacterial enhancer-binding protein (e.g. NtrC) and ATP
Q69. Which describes attenuation in the trp operon?✓ Premature transcription termination in the leader controlled by translation of two Trp codons
Q70. A reporter gene fused to a promoter is used to:✓ Quantify the promoter's activity via an easily measured product
Q71. Histone deacetylation generally:✓ Represses transcription by tightening chromatin
Q72. CpG-island promoter methylation typically leads to:✓ Stable gene silencing
Q73. Which best defines a trans-acting factor?✓ A diffusible product (usually protein/RNA) that can act on any copy of a target
Q74. Which of these is a positive regulator of the lac operon?✓ CAP (cAMP-CAP)
Q75. The two-component system transfers a signal via:✓ Autophosphorylation of a sensor histidine kinase and phosphotransfer to a response regulator
Q76. Which describes the lac operon under high glucose, no lactose?✓ Off: repressor on operator, CAP inactive
4.3 Regulation — Test 5
Q77. Which conditions give maximal lac operon expression?✓ High cAMP, no glucose, lactose present
Q78. Steroid hormone receptors, upon ligand binding, typically:✓ Translocate (if cytosolic), dimerize and bind hormone response elements to regulate transcription
Q79. Enhancers increase transcription by:✓ Binding activators and contacting the promoter via DNA looping
Q80. The Mediator complex functions to:✓ Bridge enhancer-bound activators to RNA Pol II and the basal machinery
Q81. In bacteria, which sigma factor activates nitrogen-fixation/assimilation genes?✓ σ54
Q82. Which best describes a silencer element?✓ A cis-element that, when bound by repressive factors, decreases transcription
Q83. Which DNA-binding motif is formed by two amphipathic helices that dimerize, with basic regions contacting DNA?✓ Leucine zipper (bZIP)
Q84. Which is TRUE about the operator in negative control?✓ Repressor binding to it blocks transcription
Q85. In the lac operon, IPTG works by:✓ Acting as a non-metabolizable inducer that inactivates the repressor
Q86. Eukaryotic activator proteins generally contain separable:✓ DNA-binding and activation domains
Q87. Which describes positive autoregulation?✓ A factor activates transcription of its own gene
Q88. CpG island hypomethylation at a promoter is generally associated with:✓ Active/poised transcription
Q89. Antitermination (as by λ N protein) allows RNA polymerase to:✓ Read through terminators to transcribe downstream genes
Q90. A repressible operon (e.g. trp) is turned OFF by:✓ The end product acting as a corepressor
Q91. Which experimental readout indicates a gene is transcriptionally repressed after a treatment (nuclear run-on shows signal lost)?✓ Loss of nascent (run-on) signal for that gene
Q92. The CAP-cAMP complex activates transcription by:✓ Bending DNA and making protein-protein contacts that recruit RNA polymerase
Q93. Which is an example of negative control by induction (inducible negative)?✓ lac operon
Q94. Which best describes the role of chromatin remodeling complexes in transcription?✓ They use ATP to reposition/evict nucleosomes, altering DNA accessibility
Q95. Which describes a constitutive (housekeeping) gene?✓ Expressed continuously at a relatively steady level
Q96. Differential use of sigma factors lets bacteria:✓ Redirect RNA polymerase to different promoter sets under different conditions