32 Questions
What stimulates the synthesis of enzymes involved in lactose metabolism in E. coli?
Presence of lactose
Which enzyme catalyzes the cleavage of lactose in E. coli?
β-galactosidase
What type of mutants express all three genes involved in lactose metabolism in the absence of lactose?
Constitutive mutants
What did Jacob and Monod identify as defective in regulation of the genes involved in lactose metabolism in E. coli?
Mutants
Which protein binds to the GC box and stimulates transcription?
SP-1 factor
What is the function of histone acetyltransferase (HAT)?
Stimulates transcription
What is the effect of histone acetylation on histones?
Reduces positive charge of histones
What is the role of histone deacetylase (HDAC) in transcription?
Represses transcription
Which proteins disrupt the interaction of H1 with the nucleosome, stimulating transcription?
$HMGN$ proteins
What is the function of non-denaturing gel in identifying transcription activators?
Uses electrophoresis method for identification
Which of the following is true about enhancers?
They are responsible for tissue-specific gene expression
What is the role of the Ig heavy chain enhancer?
Stimulate transcription in B lymphocytes
How are eukaryotic regulatory sequences determined?
By ligating a reporter gene to the regulatory sequence of a cloned gene and observing the activity of the reporter gene in transfected cells
What do Cis-acting Regulatory sequences do?
Regulate transcription by binding regulatory proteins
What is the function of core promoter elements, including TATA box?
Serve as a binding site for general transcription factors
Where are enhancers located?
Far from the transcription start site
How do enhancers work?
By binding transcription factors that regulate RNA polymerase II activity through DNA looping
What type of genes contain core promoter elements, including TATA box?
Genes transcribed by RNA Polymerase II
What do regulatory sequences, including enhancers, interact with?
Tissue-specific proteins
What determines whether a gene is expressed?
Regulatory sequences interacting with tissue-specific proteins
What type of sequence can enhance transcription from a promoter?
Enhancers located far from the transcription start site
In the Lac Operon of E. coli, the 'i' gene mutants result in constitutive expression due to:
Regulatory mutations in the 'i' locus
In the absence of lactose, the Lac Operon is repressed because:
The repressor binds to the operator and prevents RNA polymerase binding
The Lac Operon studies revealed that regulatory proteins interact with specific DNA sequences to control transcription in:
Both prokaryotic and eukaryotic genes
Eukaryotic transcription is more complex than prokaryotic transcription because it involves:
Multiple RNA polymerases and control at initiation and elongation stages
The cAMP + CAP complex binds to specific target DNA sequences in the Lac operon to:
Activate transcription in E. coli
Which molecule prevents the repressor from binding to the operator in the presence of lactose?
Lactose
In eukaryotes, which sequence is commonly found in the promoter region and has binding sites for transcription factors?
TATA sequence
Which enzyme is responsible for histone acetylation?
Histone acetyltransferase (HAT)
Eukaryotic RNA polymerases require specific proteins called ____________ to initiate transcription.
Activators
Which type of RNA is synthesized by eukaryotic RNA polymerases?
mRNA, rRNA, tRNA, and small RNAs
What is responsible for controlling transcription at initiation and elongation stages in eukaryotes?
Transcription factors and chromatin-modifying proteins
Study Notes
- The Lac Operon in E. coli consists of genes encoding beta-Galactosidase, permease, transacetylase, and a repressor.
- Transcription of the operon is controlled by the operator (o) located next to the transcription initiation site.
- Regulatory mutations are found in the 'o' and 'i' loci, resulting in constitutive expression in 'i' gene mutants.
- The 'i' gene product is a repressor that binds to the operator and prevents transcription when lactose is not present.
- Lactose binds to the repressor, preventing it from binding to the operator and allowing transcription.
- In the absence of lactose, the repressor binds to the operator and prevents RNA polymerase from binding to the promoter, blocking transcription.
- In the presence of lactose, the repressor is inhibited, allowing RNA polymerase to bind and stimulate transcription.
- The Lac Operon studies revealed that regulatory proteins interact with specific DNA sequences to control transcription, applicable to both prokaryotic and eukaryotic genes.
- The cAMP + CAP complex binds to specific target DNA sequences in the Lac operon to activate transcription in E. coli.
- Eukaryotic transcription is more complex, involving multiple RNA polymerases and the control of transcription at initiation and elongation stages.
- Transcription is regulated by proteins binding to specific regulatory sequences and modifying chromatin structure.
- Eukaryotic RNA polymerases require specific proteins called transcription factors to initiate transcription.
- The promoter region in eukaryotes contains a TATA sequence and binding sites for transcription factors.
- Eukaryotic RNA polymerases are responsible for the synthesis of different types of RNA including mRNA, rRNA, tRNA, and small RNAs.
Test your knowledge of transcription regulation in bacteria and eukaryotes with this quiz. Learn about the role of cis-acting regulatory sequences, promoters, enhancers, and the binding of regulatory proteins in controlling gene expression.
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