27 Questions
What did Jacob and Monod study in the 1950s?
Regulation of gene expression in E. coli
Which mutants were defective in regulation of the genes involved in lactose metabolism?
Mutants that express all three genes in the absence of lactose and mutants that cannot express these genes even in the presence of lactose
What stimulates the synthesis of enzymes involved in lactose metabolism?
Presence of Lactose
What is the role of transacetylase in lactose metabolism?
Inactivates toxic thiogalactosides
Which protein binds to the GC box and stimulates transcription?
SP-1 factor
What is the function of histone acetyltransferase (HAT) in transcription?
Stimulates transcription by acetylating histones
How do transcriptional repressors suppress transcription?
By inhibiting the binding of transcription factors or RNA polymerase to the promoter
What is the role of HMGN proteins in chromatin structure?
Connects to H1's binding site and disrupts the interaction with the nucleosome
What occurs in active chromatin due to histone acetylation?
Reduction in positive charge of histones, facilitating binding of transcription factors
What is the effect of histone modification by acetylating lysines?
Reduces positive charge of histones, weakening their binding to DNA and facilitating binding with other proteins
Which RNA polymerase in eukaryotes synthesizes ribosomal RNAs?
RNA Polymerase I
What is the function of the 'i' gene product in the Lac Operon of E. coli?
It acts as a repressor that binds to the operator and prevents transcription in the absence of lactose
What happens to the lac operon in E. coli when glucose is present?
It is repressed by glucose binding to a repressor
What type of control element are regulatory sequences like the operator in the Lac Operon?
Cis-acting control elements
What is the role of cAMP in positive control of the lac operon in E. coli?
It mediates positive control by altering the binding of the cAMP-CAP complex to the regulatory sequences of the operon
Which regulatory sequences can stimulate transcription from a distance?
Enhancers
What type of regulatory sequences determine tissue-specific gene expression in mammals?
Enhancers
Where are core promoter elements, including a TATA box, located in genes transcribed by RNA Polymerase II?
At the transcription start site
Which type of regulatory sequences can influence transcription and are located upstream of the TATA box?
Promoters
How do enhancers work to stimulate transcription?
By binding transcription factors and interacting with RNA polymerase II/mediator complex at the promoter region through DNA looping
What is the main function of transcription activators in gene expression regulation?
To control the amount of transcription and determine whether a gene is expressed
What is the method for determining eukaryotic regulatory sequences?
Introducing a cloned gene's regulatory sequence into cultured cells and observing the transcription of a reporter gene
Which type of proteins bind to Cis-acting regulatory sequences to regulate RNA Polymerase II activity?
Transcription factors
What are Cis-acting regulatory sequences responsible for?
Regulating gene expression on the same DNA molecule where their genes are located
What is the role of silencers in gene expression regulation?
To inhibit or suppress transcription from nearby promoters
Which type of regulatory sequence can be involved in both activating and repressing gene expression?
Enhancers
What is the function of upstream Cis-acting regulatory sequences located before the TATA box?
To inhibit or suppress transcription from nearby promoters
Study Notes
- Transcription in bacteria and eukaryotic cells is regulated by the binding of regulatory proteins to Cis-acting Regulatory sequences
- Eukaryotic regulatory sequences are determined by introducing a cloned gene's regulatory sequence into cultured cells and observing the transcription of a reporter gene
- Genes transcribed by RNA Polymerase II have core promoter elements, including a TATA box
- Other Cis-acting regulatory sequences are located upstream of the TATA box and can influence transcription
- Enhancers are regulatory sequences that can stimulate transcription from a distance, sometimes several kilo bases away from the transcription start site
- Enhancers work by binding transcription factors that interact with RNA polymerase II/mediator complex at the promoter region through DNA looping
- Mammalian enhancers, such as the immunoglobulin enhancer, are involved in tissue-specific gene expression
- Enhancers can control the amount of transcription, determine whether a gene is expressed, and interact with tissue-specific proteins
- Transcription of genes is controlled by proteins that bind to regulatory sequences and regulate RNA Polymerase II activity, such as transcription activators.
Test your knowledge of regulatory sequences in transcription, including cis-acting regulatory sequences, promoters, and enhancers in bacteria and eukaryotic cells.
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