Chapter 14 genetcis
What is an operon?
A cluster of genes under the transcriptional control of a single promoter
What is an enhancer?
A regulatory element that can increase the rate of transcription.
What is cyclic AMP (cAMP)?
A small effector molecule involved in the positive control of the lac operon
What is a corepressor molecule?
A small effector molecule that binds to a repressor protein
What is the advantage of operon organization in bacteria?
Bacteria can coordinate the expression of multiple genes in the same biological pathway.
regulatory transcription factors
Both positive and negative control
How does gene regulation help conserve energy for an organism?
By only expressing the gene product when it is needed in the cell.
The lac operon is also under positive control by an activator protein called what?
CAP
How does allolactose affect the lac repressor protein?
It binds to the repressor protein and prevents it from binding to the operator site of the lac operon.
What is the effect of low levels of tryptophan on the transcription of the trp operon?
Low levels of tryptophan will result in high levels of transcription.
Which of the following is a common modification that affects the structure of DNA?
Methylation
What does the lac operon region contain?
Promoter, operator, and three structural genes
What are regulatory transcription factors?
Proteins that bind to DNA and affect the transcription of one or more genes
What is cell differentiation?
The process by which cells become specialized in different types
At what levels does gene regulation occur in prokaryotes?
Transcription Translation Post-translation
What are the three features common to most promoters that are needed for the initiation of transcription of protein coding genes in eukaryotes?
Transcriptional start site TATA box Regulatory elements
Polycistronic mRNA:
encodes more than one protein
A small effector molecule that increases the rate of transcription is called a(n) ___
inducer
In the lac operon, the _______ is the DNA sequence at which the lac repressor binds.
operator
The lacO site of the lac operon is called the ___ and is the site where the repressor protein binds.
operator
How do activator proteins diminish the level of chromatin compaction at the site of the gene that is to be transcribed?
Activators bind to an enhancer site and then recruit other proteins to unravel and loosen the packed chromatin.
Which of the following is a form of gene regulation in which a eukaryotic pre-mRNA can be processed to produce more than one mature RNA?
Alternative splicing
When are the genes involved in lactose metabolism in E. coli expressed and when are they turned off?
The genes for lactose metabolism are expressed when lactose is present but not when it is absent.
What is basal transcription?
The low level of transcription activated by the core promoter alone
Which of the following are key differences between eukaryotic and prokaryotic transcriptional regulation?
The majority of genes are organized individually in eukaryotes, but are organized as operons in prokaryotes. Combinatorial control of gene expression is more common in eukaryotes. The complexity of eukaryotic development requires that transcription be more coordinated and integrated than in prokaryotes.
What is the inducer molecule for the lac operon?
allolactose
Regulation of prokaryotic gene expression typically involves all of the following mechanisms EXCEPT:
regulation of RNA processing
The enzyme___ ___ is responsible for covalently attaching methyl groups to DNA.
DNA methyltransferase
______ is the main protein that delivers oxygen to cells of a mammal's body.
Hemoglobin
The lac operon is an example of what type of operon?
Inducible operon
Which of the following are similarities between eukaryotic and prokaryotic transcriptional regulation?
Proteins influence the ability of RNA polymerase to bind to the DNA. Small effector molecules are involved in gene regulation.
The lac repressor protein prevents the ___ ____enzyme from transcribing the genes in the lac operon.
RNA polymearse
Why are interactions between RNA polymerase II and GTFs important for transcription in eukaryotes?
RNA polymerase II and GTFs must interact for the polymerase to bind properly at the core promoter site of the DNA.
Match each protein or group of proteins with its role in transcription.
RNA polymerase: synthesis of RNA from a DNA template general transcription factors required for binding to the core promoter and initiating transcription activators: binding to enhancer sequences and interaction with other proteins
What are silencers?
Regulatory elements that can prevent or decrease transcription.
Which of the following are proteins involved in regulating the rate of transcription in eukaryotes?
Repressors Activators
______ are regulatory DNA elements that can prevent or decrease the rate of transcription of a gene.
Silencers
What are the two components of the core promoter?
TATA box transcriptional start site
In order for transcription of protein coding genes in eukaryotes to begin, the promoter must have several key features. What are they?
TATA box, regulatory elements, transcriptional start site
What is chromatin?
The complex formed by DNA and its associated proteins
Which of the following are key differences between eukaryotic and prokaryotic transcriptional regulation?
The complexity of eukaryotic development requires that transcription be more coordinated and integrated than in prokaryotes. The majority of genes are organized individually in eukaryotes, but are organized as operons in prokaryotes. Combinatorial control of gene expression is more common in eukaryotes.
What is the role of the corepressor in the expression of the trp operon?
The corepressor binds to the repressor protein and causes a conformational change, which allows the repressor to bind to the operator site.
What is the function of the genes that are expressed in the lac operon of E. coli?
The metabolism of lactose
The binding of the corepressor to the trp repressor results in what?
The repressor binds to the operator and prevents transcription.
What is the role of the repressor protein in the transcription of the trp operon?
The repressor protein binds to the operator site and prevents the transcription of the trp operon.
What is the CAP site for the lac operon?
The sequence of nucleotides that is recognized by an activator protein
The molecule that serves as the inducer of the lac operon is__
allolactose
When the sugar___ binds to the repressor protein, this causes a conformational change that prevents the repressor from binding to the ___ site.
allolactose operator
The process whereby different transcripts are made from a single gene is called ___ ___
alternative splicing
In eukaryotes, the core promoter, by itself, results in low levels of transcription that is known as ___ transcription.
basal
When __ binds to CAP, the resulting complex binds to the CAP site near the lac___ . This causes a bend in the DNA that enhances the ability of RNA polymerase to bind, and so the transcription rate is increased.
cAMP Promoter
How does cAMP play a role in the transcription of the lac operon?
cAMP binds to CAP and together they bind to the DNA, which enhances transcription of the lac operon.
When cAMP binds to a protein called___ , it enhances the transcription of the genes of the lac operon.
cap
Proteins that use energy from ATP hydrolysis to change the locations and compositions of nucleosomes are called ATP-dependent - ___ ___ complexes.
chromatic remodeling
DNA and its associated proteins form a compact structure called:
chromatin
A small effector molecule that binds to a repressor protein and decreases the rate of transcription is called a(n):
corepressor
Cell ______ is the process by which cells become specialized into particular types.
differentiation
In eukaryotic DNA, regulatory elements known as ___ play a role in the ability of RNA polymerase to begin transcription, thereby increasing the rate of transcription.
enhancers
The process in which the information in a gene is made into a functional gene product, such as an RNA molecule or a protein, is termed gene ___
expression
Many eukaryotic genes are flanked by a nucleosome- ___ ___ , which is a site that is missing nucleosomes.
free region
The functional product of genes arises from what process?
gene expression.
Transcription of the trp operon is ______ when levels of tryptophan are low in the cell.
increased
In mammals, when iron levels are high, iron binds to the iron regulatory protein, which results in:
increased translation of ferritin
An operon that can be turned on in the presence of a small effector molecule is said to be a(n) ___ operon.
inducible
This diagram is a representation of which type of operon?
lac operon in the presence of lactose
Which of the following genes encodes the lac repressor protein?
lacI
What are the basic components of the lac operon?
lacY promoter lacA lacZ
Histone modifications can result in:
loosening of chromatin activation of transcription
What is the effect of high levels of tryptophan on the transcription of the trp operon?
low levels
Bacteria and eukaryotes can regulate genes at the level of transcription. In eukaryotes, gene expression is also commonly regulated at the levels of RNA ___ and translation.
modification
____ control is transcriptional regulation by repressor proteins.
negative
Repressor proteins are used for____ control of gene expression, and activator proteins are used for_____ control of gene expression.
negative positive
The lacO site of the lac operon is called the___ and is the site where the repressor protein binds.
operator
A(n) __ is a cluster of genes that are part of a single transcription unit that is under the control of a single promoter.
operon
An mRNA that encodes more than one protein is called ___ mRNA.
polycistronic
The catabolite activator protein (CAP) is involved in ______ control of the lac operon.
positive
The protein encoded by the lacI gene functions to:
prevent transcription of the lac operon
Regulatory transcription factors influence the expression of genes by binding directly to DNA at or near the___ site and affect the rate of transcription.
promoter
Histone modifications primarily affect:
the degree of chromatin compaction
The transcription of the lac operon genes is inhibited when the lac repressor protein binds to:
the lac operator
The function of the protein encoded by lacI is:
to repress transcription of the lac operon
Eukaryotic gene expression can be regulated at which levels?
transcription translation RNA modification
The genes in the trp operon encode enzymes that make the amino acid__ .
tryptophan
What is the function of the genes encoded by the trp operon?
The synthesis of the amino acid tryptophan
An activator protein recognizes the ______ of the lac operon.
CAP site
What small effector molecule is involved in the activation of the lac operon when glucose is absent?
Cyclic adenosine monophosphate cyclic AMP CyclicAMP Cyclic-AMP cAMP
What is the function of ATP-dependent chromatin-remodeling complexes?
They cause a change in the locations and/or compositions of nucleosomes
How do CAP and cAMP increase the transcription of the lac operon?
When CAP and cAMP bind to the CAP site, this enhances binding of RNA polymerase to the promoter site
Under what conditions does the lac repressor bind to the operator of the lac operon and prevent transcription?
When the concentration of lactose is low in the cell
A nucleosome-free region (NFR) is:
a site on a chromosome that is missing nucleosomes
In eukaryotes, the rate of transcription of genes is influenced by regulatory transcription factors called ___ and ___ . These proteins bind to regulatory elements and control the gene expression rate.
activators repressors
Operons enable bacteria to
coordinate the regulation of genes with related functions
How does the presence of lactose in the cell influence the transcription of the lac operon?
When lactose is present, transcription of the lac operon is high. When lactose is present, the lac repressor protein does not bind to the operator site and transcription can occur.
The lacI gene encodes the lac
repressor
The trp operon is regulated by a(n) ___protein that is encoded by the trpR gene.
repressor