Gene Regulation (Promoters/ Operators) Flashcards
What is a gene?
A specific sequence of nucleotides in DNA or RNA that codes for a product that provides a function for the organism.
What marks the beginning of a gene in DNA?
Promoter.
What are the two short sequences contained in a promoter?
- -10: TATAAT
- -35: TTGACA
What binds to the promoter to start transcription of the gene?
RNA Polymerase.
What is the operator in gene regulation?
Region of DNA between promoter and gene where a repressor protein can bind.
True or False: The binding of a repressor to the operator always occurs.
False.
What is quorum sensing?
Cell–cell communication in bacteria achieved through the accumulation of signaling molecules.
What is an operon?
A group of genes that participate in the same metabolic activity.
What is the primary metabolic activity controlled by the lac operon?
Lactose catabolism.
What are the three genes in the lac operon?
- lacZ
- lacY
- lacA
What prevents RNA polymerase from binding to the promoter in the lac operon?
Lac repressor protein.
What promotes transcription in the lac operon?
Catabolite activator protein (CAP).
What derivative of lactose inhibits the lac repressor?
Allolactose.
What type of regulation does the lac operon experience?
Both positive and negative signals.
Fill in the blank: Lactose positively regulates the lac operon, while _______ negatively regulates it.
Glucose.
What complex binds to the lac promoter region and stimulates transcription?
cAMP–CRP complex.
What molecule binds to the promoter site of the lac operon for effective transcription?
Catabolite activator protein.
How does glucose indirectly affect the transcription of the lac operon?
Low levels of glucose upregulate the transcription of this operon.
What is a promoter in gene regulation?
A promoter is a DNA sequence that initiates transcription of a gene.
True or False: Operators are found downstream of promoters.
False: Operators are typically found downstream of the promoter but can also be located within the promoter region.
Fill in the blank: The __________ is a region of DNA where RNA polymerase binds to initiate transcription.
promoter
What role do operators play in gene regulation?
Operators serve as binding sites for repressor proteins that inhibit transcription.
Which of the following is NOT a component of gene regulation? A) Promoter B) Operator C) Ribosome
C) Ribosome
What is the function of a repressor protein?
A repressor protein binds to the operator to prevent transcription.
True or False: Enhancers are the same as promoters.
False: Enhancers are regulatory sequences that can enhance the transcription of a gene but are not the same as promoters.
What is the basic function of RNA polymerase in relation to promoters?
RNA polymerase binds to the promoter to initiate the transcription of DNA into RNA.
What is an example of a prokaryotic operon?
The lac operon is an example of a prokaryotic operon.
Fill in the blank: In the lac operon, the presence of __________ causes the repressor to release from the operator.
lactose
What is the purpose of a transcription factor?
Transcription factors help regulate the transcription process by binding to specific DNA sequences.
True or False: Promoters are always located at the start of a gene.
True
What type of RNA is produced during transcription?
Messenger RNA (mRNA)
What are cis-regulatory elements?
Cis-regulatory elements are regions of non-coding DNA that regulate the transcription of nearby genes.
Fill in the blank: The __________ is a DNA sequence that can enhance transcription from a distance.
enhancer
What does the term ‘operon’ refer to?
An operon is a cluster of genes under the control of a single promoter and regulated together.
True or False: All genes have both a promoter and an operator.
False: Not all genes have an operator; it is characteristic of operons.
What is the role of an activator in gene regulation?
An activator enhances the binding of RNA polymerase to the promoter, increasing transcription.
What is the significance of the TATA box?
The TATA box is a conserved DNA sequence found in many promoters that helps initiate transcription.
Fill in the blank: In eukaryotic cells, promoters often contain __________ elements that help regulate transcription.
core
What is a common characteristic of prokaryotic promoters?
Prokaryotic promoters typically have a conserved sequence known as the -10 and -35 regions.
True or False: Operators can be found in eukaryotic gene regulation.
True: Eukaryotic genes can have operator-like sequences, though they are generally less characterized.
What does it mean for a promoter to be ‘constitutive’?
A constitutive promoter is always active and drives constant expression of the gene.
Multiple Choice: What is the primary function of the sigma factor in prokaryotic transcription? A) To bind to the promoter B) To initiate translation C) To splice mRNA
A) To bind to the promoter
What is the difference between a strong and weak promoter?
A strong promoter has a high affinity for RNA polymerase, leading to high levels of transcription, while a weak promoter has a lower affinity.
True or False: The lac operon is an example of negative control in gene regulation.
True
What is the function of the CAP protein in the lac operon?
CAP (catabolite activator protein) enhances the transcription of the lac operon in the presence of cAMP.
Fill in the blank: The __________ is a sequence that can bind transcription factors to regulate gene expression.
promoter
What does ‘transcriptional activation’ refer to?
Transcriptional activation refers to the process of increasing gene expression through various regulatory mechanisms.
True or False: All genes are regulated by both promoters and operators.
False
What is the role of histone modification in gene regulation?
Histone modification can alter the accessibility of DNA for transcription and thus regulate gene expression.
Fill in the blank: __________ are sequences that can repress gene expression by binding to operators.
Repressors
What is the role of chromatin remodeling in gene regulation?
Chromatin remodeling alters the structure of chromatin to allow or restrict access to DNA for transcription.
Multiple Choice: Which of the following is a feature of eukaryotic promoters? A) Operons B) TATA box C) Sigma factor
B) TATA box
What does the term ‘negative feedback’ mean in the context of gene regulation?
Negative feedback refers to a mechanism where the product of a gene inhibits its own expression.
True or False: Inducible operons are usually off and can be turned on in response to specific signals.
True
What is the main difference between a repressible operon and an inducible operon?
A repressible operon is usually on and can be turned off, while an inducible operon is usually off and can be turned on.
Fill in the blank: The __________ is a protein that binds to the operator to block transcription.
repressor
What is the significance of the -10 and -35 regions in prokaryotic promoters?
They are conserved sequences that help RNA polymerase identify the correct initiation site for transcription.
True or False: Gene regulation only occurs at the transcriptional level.
False: Gene regulation can occur at multiple levels, including transcriptional, post-transcriptional, and translational.
What is the purpose of alternative splicing in gene regulation?
Alternative splicing allows for the production of multiple protein isoforms from a single gene, influencing gene expression.
Fill in the blank: __________ are sequences that can enhance transcription by binding to activators.
Enhancers
What is the role of the promoter-proximal region?
The promoter-proximal region contains regulatory elements that influence the efficiency of transcription initiation.
What is the function of transcriptional coactivators?
Coactivators assist transcription factors in increasing the rate of transcription without directly binding to DNA.
